Merge pull request 'CONDSTORE' (#71) from feat/condstore-try-2 into main

Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/aerogramme/pulls/71

18 files changed, 801 insertions, 258 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 2c264f2..e00317b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1806,8 +1806,8 @@ dependencies = [
 
 [[package]]
 name = "imap-codec"
-version = "1.0.0"
-source = "git+https://github.com/duesee/imap-codec?branch=v2#1f490146bb6197eee6032205e3aa7f297efd9b39"
+version = "2.0.0"
+source = "git+https://github.com/superboum/imap-codec?branch=custom/aerogramme#b0a80c4826f3d8bf2d2e69f68443c261e62bb40f"
 dependencies = [
  "abnf-core",
  "base64 0.21.5",
@@ -1822,7 +1822,7 @@ dependencies = [
 [[package]]
 name = "imap-flow"
 version = "0.1.0"
-source = "git+https://github.com/duesee/imap-flow.git?rev=e45ce7bb6ab6bda3c71a0c7b05e9b558a5902e90#e45ce7bb6ab6bda3c71a0c7b05e9b558a5902e90"
+source = "git+https://github.com/superboum/imap-flow.git?branch=custom/aerogramme#0f548a2070aace09f9f9a0b6ef221efefb8b110b"
 dependencies = [
  "bounded-static",
  "bytes",
@@ -1833,8 +1833,8 @@ dependencies = [
 
 [[package]]
 name = "imap-types"
-version = "1.0.0"
-source = "git+https://github.com/duesee/imap-codec?branch=v2#1f490146bb6197eee6032205e3aa7f297efd9b39"
+version = "2.0.0"
+source = "git+https://github.com/superboum/imap-codec?branch=custom/aerogramme#b0a80c4826f3d8bf2d2e69f68443c261e62bb40f"
 dependencies = [
  "base64 0.21.5",
  "bounded-static",
diff --git a/Cargo.toml b/Cargo.toml
index 68a46e3..55f0284 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -58,14 +58,14 @@ aws-sdk-s3 = "1.9.0"
 eml-codec = { git = "https://git.deuxfleurs.fr/Deuxfleurs/eml-codec.git", branch = "main" }
 smtp-message = { git = "http://github.com/Alexis211/kannader", branch = "feature/lmtp" }
 smtp-server = { git = "http://github.com/Alexis211/kannader", branch = "feature/lmtp" }
-imap-codec = { version = "1.0.0", features = ["bounded-static", "ext_condstore_qresync"] }
-imap-flow = { git = "https://github.com/duesee/imap-flow.git", rev = "e45ce7bb6ab6bda3c71a0c7b05e9b558a5902e90" }
+imap-codec = { version = "2.0.0", features = ["bounded-static", "ext_condstore_qresync"] }
+imap-flow = { git = "https://github.com/superboum/imap-flow.git", branch = "custom/aerogramme" }
 
 [dev-dependencies]
 
 [patch.crates-io]
-imap-types = { git = "https://github.com/duesee/imap-codec", branch = "v2" }
-imap-codec = { git = "https://github.com/duesee/imap-codec", branch = "v2" }
+imap-types = { git = "https://github.com/superboum/imap-codec", branch = "custom/aerogramme" }
+imap-codec = { git = "https://github.com/superboum/imap-codec", branch = "custom/aerogramme" }
 
 [[test]]
 name = "behavior"
diff --git a/src/imap/attributes.rs b/src/imap/attributes.rs
index cf7cb52..d094f1a 100644
--- a/src/imap/attributes.rs
+++ b/src/imap/attributes.rs
@@ -1,4 +1,5 @@
 use imap_codec::imap_types::fetch::{MacroOrMessageDataItemNames, MessageDataItemName, Section};
+use imap_codec::imap_types::command::FetchModifier;
 
 /// Internal decisions based on fetched attributes
 /// passed by the client
@@ -7,7 +8,7 @@ pub struct AttributesProxy {
     pub attrs: Vec<MessageDataItemName<'static>>,
 }
 impl AttributesProxy {
-    pub fn new(attrs: &MacroOrMessageDataItemNames<'static>, is_uid_fetch: bool) -> Self {
+    pub fn new(attrs: &MacroOrMessageDataItemNames<'static>, modifiers: &[FetchModifier], is_uid_fetch: bool) -> Self {
         // Expand macros
         let mut fetch_attrs = match attrs {
             MacroOrMessageDataItemNames::Macro(m) => {
@@ -31,9 +32,23 @@ impl AttributesProxy {
             fetch_attrs.push(MessageDataItemName::Uid);
         }
 
+        // Handle inferred MODSEQ tag
+        let is_changed_since = modifiers
+            .iter()
+            .any(|m| matches!(m, FetchModifier::ChangedSince(..)));
+        if is_changed_since && !fetch_attrs.contains(&MessageDataItemName::ModSeq) {
+            fetch_attrs.push(MessageDataItemName::ModSeq);
+        }
+
         Self { attrs: fetch_attrs }
     }
 
+    pub fn is_enabling_condstore(&self) -> bool {
+        self.attrs.iter().any(|x| {
+            matches!(x, MessageDataItemName::ModSeq)
+        })
+    }
+
     pub fn need_body(&self) -> bool {
         self.attrs.iter().any(|x| {
             match x {
diff --git a/src/imap/capability.rs b/src/imap/capability.rs
index feadb6b..6533ccb 100644
--- a/src/imap/capability.rs
+++ b/src/imap/capability.rs
@@ -1,8 +1,11 @@
+use imap_codec::imap_types::command::{FetchModifier, StoreModifier, SelectExamineModifier};
 use imap_codec::imap_types::core::NonEmptyVec;
 use imap_codec::imap_types::extensions::enable::{CapabilityEnable, Utf8Kind};
 use imap_codec::imap_types::response::Capability;
 use std::collections::HashSet;
 
+use crate::imap::attributes::AttributesProxy;
+
 fn capability_unselect() -> Capability<'static> {
     Capability::try_from("UNSELECT").unwrap()
 }
@@ -11,9 +14,11 @@ fn capability_condstore() -> Capability<'static> {
     Capability::try_from("CONDSTORE").unwrap()
 }
 
+/*
 fn capability_qresync() -> Capability<'static> {
     Capability::try_from("QRESYNC").unwrap()
 }
+*/
 
 #[derive(Debug, Clone)]
 pub struct ServerCapability(HashSet<Capability<'static>>);
@@ -26,7 +31,7 @@ impl Default for ServerCapability {
             Capability::Move,
             Capability::LiteralPlus,
             capability_unselect(),
-            //capability_condstore(),
+            capability_condstore(),
             //capability_qresync(),
         ]))
     }
@@ -48,15 +53,29 @@ impl ServerCapability {
     }
 }
 
-enum ClientStatus {
+#[derive(Clone)]
+pub enum ClientStatus {
     NotSupportedByServer,
     Disabled,
     Enabled,
 }
+impl ClientStatus {
+    pub fn is_enabled(&self) -> bool {
+        matches!(self, Self::Enabled)
+    }
+
+    pub fn enable(&self) -> Self {
+        match self {
+            Self::Disabled => Self::Enabled,
+            other => other.clone(),
+        }
+    }
+}
+
 
 pub struct ClientCapability {
-    condstore: ClientStatus,
-    utf8kind: Option<Utf8Kind>,
+    pub condstore: ClientStatus,
+    pub utf8kind: Option<Utf8Kind>,
 }
 
 impl ClientCapability {
@@ -70,6 +89,36 @@ impl ClientCapability {
         }
     }
 
+    pub fn enable_condstore(&mut self) {
+        self.condstore = self.condstore.enable();
+    }
+
+    pub fn attributes_enable(&mut self, ap: &AttributesProxy) {
+        if ap.is_enabling_condstore() {
+            self.enable_condstore()
+        }
+    }
+
+    pub fn fetch_modifiers_enable(&mut self, mods: &[FetchModifier]) {
+        if mods.iter().any(|x| matches!(x, FetchModifier::ChangedSince(..))) {
+            self.enable_condstore()
+        }
+    }
+
+    pub fn store_modifiers_enable(&mut self, mods: &[StoreModifier]) {
+        if mods.iter().any(|x| matches!(x, StoreModifier::UnchangedSince(..))) {
+            self.enable_condstore()
+        }
+    }
+
+    pub fn select_enable(&mut self, mods: &[SelectExamineModifier]) {
+        for m in mods.iter() {
+            match m {
+                SelectExamineModifier::Condstore => self.enable_condstore(),
+            }
+        }
+    }
+
     pub fn try_enable(
         &mut self,
         caps: &[CapabilityEnable<'static>],
diff --git a/src/imap/command/authenticated.rs b/src/imap/command/authenticated.rs
index 1481a80..9b6bb24 100644
--- a/src/imap/command/authenticated.rs
+++ b/src/imap/command/authenticated.rs
@@ -2,7 +2,7 @@ use std::collections::BTreeMap;
 use std::sync::Arc;
 
 use anyhow::{anyhow, bail, Result};
-use imap_codec::imap_types::command::{Command, CommandBody};
+use imap_codec::imap_types::command::{Command, CommandBody, SelectExamineModifier};
 use imap_codec::imap_types::core::{Atom, Literal, NonEmptyVec, QuotedChar};
 use imap_codec::imap_types::datetime::DateTime;
 use imap_codec::imap_types::extensions::enable::CapabilityEnable;
@@ -58,8 +58,8 @@ pub async fn dispatch<'a>(
         } => ctx.status(mailbox, item_names).await,
         CommandBody::Subscribe { mailbox } => ctx.subscribe(mailbox).await,
         CommandBody::Unsubscribe { mailbox } => ctx.unsubscribe(mailbox).await,
-        CommandBody::Select { mailbox } => ctx.select(mailbox).await,
-        CommandBody::Examine { mailbox } => ctx.examine(mailbox).await,
+        CommandBody::Select { mailbox, modifiers } => ctx.select(mailbox, modifiers).await,
+        CommandBody::Examine { mailbox, modifiers } => ctx.examine(mailbox, modifiers).await,
         CommandBody::Append {
             mailbox,
             flags,
@@ -292,7 +292,7 @@ impl<'a> AuthenticatedContext<'a> {
             }
         };
 
-        let view = MailboxView::new(mb).await;
+        let view = MailboxView::new(mb, self.client_capabilities.condstore.is_enabled()).await;
 
         let mut ret_attrs = vec![];
         for attr in attributes.iter() {
@@ -311,8 +311,9 @@ impl<'a> AuthenticatedContext<'a> {
                     bail!("quota not implemented, can't return freed storage after EXPUNGE will be run");
                 },
                 StatusDataItemName::HighestModSeq => {
-                    bail!("highestmodseq not yet implemented");
-                }
+                    self.client_capabilities.enable_condstore();
+                    StatusDataItem::HighestModSeq(view.highestmodseq().get())
+                },
             });
         }
 
@@ -404,6 +405,7 @@ impl<'a> AuthenticatedContext<'a> {
                           it is therefore correct to not return it even if there are unseen messages
       RFC9051 (imap4rev2) says that OK [UNSEEN] responses are deprecated after SELECT and EXAMINE
       For Aerogramme, we just don't send the OK [UNSEEN], it's correct to do in both specifications.
+    
 
     20 select "INBOX.achats"
     * FLAGS (\Answered \Flagged \Deleted \Seen \Draft $Forwarded JUNK $label1)
@@ -420,7 +422,10 @@ impl<'a> AuthenticatedContext<'a> {
     async fn select(
         self,
         mailbox: &MailboxCodec<'a>,
+        modifiers: &[SelectExamineModifier],
     ) -> Result<(Response<'static>, flow::Transition)> {
+        self.client_capabilities.select_enable(modifiers);
+
         let name: &str = MailboxName(mailbox).try_into()?;
 
         let mb_opt = self.user.open_mailbox(&name).await?;
@@ -438,7 +443,7 @@ impl<'a> AuthenticatedContext<'a> {
         };
         tracing::info!(username=%self.user.username, mailbox=%name, "mailbox.selected");
 
-        let mb = MailboxView::new(mb).await;
+        let mb = MailboxView::new(mb, self.client_capabilities.condstore.is_enabled()).await;
         let data = mb.summary()?;
 
         Ok((
@@ -455,7 +460,10 @@ impl<'a> AuthenticatedContext<'a> {
     async fn examine(
         self,
         mailbox: &MailboxCodec<'a>,
+        modifiers: &[SelectExamineModifier],
     ) -> Result<(Response<'static>, flow::Transition)> {
+        self.client_capabilities.select_enable(modifiers);
+
         let name: &str = MailboxName(mailbox).try_into()?;
 
         let mb_opt = self.user.open_mailbox(&name).await?;
@@ -473,7 +481,7 @@ impl<'a> AuthenticatedContext<'a> {
         };
         tracing::info!(username=%self.user.username, mailbox=%name, "mailbox.examined");
 
-        let mb = MailboxView::new(mb).await;
+        let mb = MailboxView::new(mb, self.client_capabilities.condstore.is_enabled()).await;
         let data = mb.summary()?;
 
         Ok((
@@ -496,7 +504,7 @@ impl<'a> AuthenticatedContext<'a> {
     ) -> Result<(Response<'static>, flow::Transition)> {
         let append_tag = self.req.tag.clone();
         match self.append_internal(mailbox, flags, date, message).await {
-            Ok((_mb, uidvalidity, uid)) => Ok((
+            Ok((_mb, uidvalidity, uid, _modseq)) => Ok((
                 Response::build()
                     .tag(append_tag)
                     .message("APPEND completed")
@@ -537,7 +545,7 @@ impl<'a> AuthenticatedContext<'a> {
         flags: &[Flag<'a>],
         date: &Option<DateTime>,
         message: &Literal<'a>,
-    ) -> Result<(Arc<Mailbox>, ImapUidvalidity, ImapUidvalidity)> {
+    ) -> Result<(Arc<Mailbox>, ImapUidvalidity, ImapUid, ModSeq)> {
         let name: &str = MailboxName(mailbox).try_into()?;
 
         let mb_opt = self.user.open_mailbox(&name).await?;
@@ -555,9 +563,9 @@ impl<'a> AuthenticatedContext<'a> {
         let flags = flags.iter().map(|x| x.to_string()).collect::<Vec<_>>();
         // TODO: filter allowed flags? ping @Quentin
 
-        let (uidvalidity, uid) = mb.append(msg, None, &flags[..]).await?;
+        let (uidvalidity, uid, modseq) = mb.append(msg, None, &flags[..]).await?;
 
-        Ok((mb, uidvalidity, uid))
+        Ok((mb, uidvalidity, uid, modseq))
     }
 }
 
diff --git a/src/imap/command/examined.rs b/src/imap/command/examined.rs
index 3dd11e2..9fc0990 100644
--- a/src/imap/command/examined.rs
+++ b/src/imap/command/examined.rs
@@ -1,16 +1,18 @@
 use std::sync::Arc;
+use std::num::NonZeroU64;
 
 use anyhow::Result;
-use imap_codec::imap_types::command::{Command, CommandBody};
+use imap_codec::imap_types::command::{Command, CommandBody, FetchModifier};
 use imap_codec::imap_types::core::Charset;
 use imap_codec::imap_types::fetch::MacroOrMessageDataItemNames;
 use imap_codec::imap_types::search::SearchKey;
 use imap_codec::imap_types::sequence::SequenceSet;
 
+use crate::imap::attributes::AttributesProxy;
 use crate::imap::capability::{ClientCapability, ServerCapability};
 use crate::imap::command::{anystate, authenticated};
 use crate::imap::flow;
-use crate::imap::mailbox_view::MailboxView;
+use crate::imap::mailbox_view::{MailboxView, UpdateParameters};
 use crate::imap::response::Response;
 use crate::mail::user::User;
 
@@ -37,8 +39,9 @@ pub async fn dispatch(ctx: ExaminedContext<'_>) -> Result<(Response<'static>, fl
         CommandBody::Fetch {
             sequence_set,
             macro_or_item_names,
+            modifiers,
             uid,
-        } => ctx.fetch(sequence_set, macro_or_item_names, uid).await,
+        } => ctx.fetch(sequence_set, macro_or_item_names, modifiers, uid).await,
         CommandBody::Search {
             charset,
             criteria,
@@ -88,17 +91,33 @@ impl<'a> ExaminedContext<'a> {
         self,
         sequence_set: &SequenceSet,
         attributes: &'a MacroOrMessageDataItemNames<'static>,
+        modifiers: &[FetchModifier],
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
-        match self.mailbox.fetch(sequence_set, attributes, uid).await {
-            Ok(resp) => Ok((
-                Response::build()
-                    .to_req(self.req)
-                    .message("FETCH completed")
-                    .set_body(resp)
-                    .ok()?,
-                flow::Transition::None,
-            )),
+        let ap = AttributesProxy::new(attributes, modifiers, *uid);
+        let mut changed_since: Option<NonZeroU64> = None;
+        modifiers.iter().for_each(|m| match m {
+            FetchModifier::ChangedSince(val) => {
+                changed_since = Some(*val);
+            },
+        });
+
+        match self.mailbox.fetch(sequence_set, &ap, changed_since, uid).await {
+            Ok(resp) => {
+                // Capabilities enabling logic only on successful command
+                // (according to my understanding of the spec)
+                self.client_capabilities.attributes_enable(&ap);
+                self.client_capabilities.fetch_modifiers_enable(modifiers);
+
+                Ok((
+                    Response::build()
+                        .to_req(self.req)
+                        .message("FETCH completed")
+                        .set_body(resp)
+                        .ok()?,
+                    flow::Transition::None,
+                ))
+            },
             Err(e) => Ok((
                 Response::build()
                     .to_req(self.req)
@@ -115,7 +134,10 @@ impl<'a> ExaminedContext<'a> {
         criteria: &SearchKey<'a>,
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
-        let found = self.mailbox.search(charset, criteria, *uid).await?;
+        let (found, enable_condstore) = self.mailbox.search(charset, criteria, *uid).await?;
+        if enable_condstore {
+            self.client_capabilities.enable_condstore();
+        }
         Ok((
             Response::build()
                 .to_req(self.req)
@@ -127,9 +149,9 @@ impl<'a> ExaminedContext<'a> {
     }
 
     pub async fn noop(self) -> Result<(Response<'static>, flow::Transition)> {
-        self.mailbox.0.mailbox.force_sync().await?;
+        self.mailbox.internal.mailbox.force_sync().await?;
 
-        let updates = self.mailbox.update().await?;
+        let updates = self.mailbox.update(UpdateParameters::default()).await?;
         Ok((
             Response::build()
                 .to_req(self.req)
diff --git a/src/imap/command/selected.rs b/src/imap/command/selected.rs
index 35c3eb4..c13b71a 100644
--- a/src/imap/command/selected.rs
+++ b/src/imap/command/selected.rs
@@ -1,7 +1,8 @@
 use std::sync::Arc;
+use std::num::NonZeroU64;
 
 use anyhow::Result;
-use imap_codec::imap_types::command::{Command, CommandBody};
+use imap_codec::imap_types::command::{Command, CommandBody, FetchModifier, StoreModifier};
 use imap_codec::imap_types::core::Charset;
 use imap_codec::imap_types::fetch::MacroOrMessageDataItemNames;
 use imap_codec::imap_types::flag::{Flag, StoreResponse, StoreType};
@@ -13,9 +14,9 @@ use imap_codec::imap_types::sequence::SequenceSet;
 use crate::imap::capability::{ClientCapability, ServerCapability};
 use crate::imap::command::{anystate, authenticated, MailboxName};
 use crate::imap::flow;
-use crate::imap::mailbox_view::MailboxView;
+use crate::imap::mailbox_view::{MailboxView, UpdateParameters};
 use crate::imap::response::Response;
-
+use crate::imap::attributes::AttributesProxy;
 use crate::mail::user::User;
 
 pub struct SelectedContext<'a> {
@@ -43,8 +44,9 @@ pub async fn dispatch<'a>(
         CommandBody::Fetch {
             sequence_set,
             macro_or_item_names,
+            modifiers,
             uid,
-        } => ctx.fetch(sequence_set, macro_or_item_names, uid).await,
+        } => ctx.fetch(sequence_set, macro_or_item_names, modifiers, uid).await,
         CommandBody::Search {
             charset,
             criteria,
@@ -56,8 +58,9 @@ pub async fn dispatch<'a>(
             kind,
             response,
             flags,
+            modifiers,
             uid,
-        } => ctx.store(sequence_set, kind, response, flags, uid).await,
+        } => ctx.store(sequence_set, kind, response, flags, modifiers, uid).await,
         CommandBody::Copy {
             sequence_set,
             mailbox,
@@ -113,17 +116,34 @@ impl<'a> SelectedContext<'a> {
         self,
         sequence_set: &SequenceSet,
         attributes: &'a MacroOrMessageDataItemNames<'static>,
+        modifiers: &[FetchModifier],
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
-        match self.mailbox.fetch(sequence_set, attributes, uid).await {
-            Ok(resp) => Ok((
-                Response::build()
-                    .to_req(self.req)
-                    .message("FETCH completed")
-                    .set_body(resp)
-                    .ok()?,
-                flow::Transition::None,
-            )),
+        let ap = AttributesProxy::new(attributes, modifiers, *uid);
+        let mut changed_since: Option<NonZeroU64> = None;
+        modifiers.iter().for_each(|m| match m {
+            FetchModifier::ChangedSince(val) => {
+                changed_since = Some(*val);
+            },
+        });
+
+        match self.mailbox.fetch(sequence_set, &ap, changed_since, uid).await {
+            Ok(resp) => {
+                // Capabilities enabling logic only on successful command
+                // (according to my understanding of the spec)
+                self.client_capabilities.attributes_enable(&ap);
+                self.client_capabilities.fetch_modifiers_enable(modifiers);
+
+                // Response to the client
+                Ok((
+                    Response::build()
+                        .to_req(self.req)
+                        .message("FETCH completed")
+                        .set_body(resp)
+                        .ok()?,
+                    flow::Transition::None,
+                ))
+            },
             Err(e) => Ok((
                 Response::build()
                     .to_req(self.req)
@@ -140,7 +160,10 @@ impl<'a> SelectedContext<'a> {
         criteria: &SearchKey<'a>,
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
-        let found = self.mailbox.search(charset, criteria, *uid).await?;
+        let (found, enable_condstore) = self.mailbox.search(charset, criteria, *uid).await?;
+        if enable_condstore {
+            self.client_capabilities.enable_condstore();
+        }
         Ok((
             Response::build()
                 .to_req(self.req)
@@ -152,9 +175,9 @@ impl<'a> SelectedContext<'a> {
     }
 
     pub async fn noop(self) -> Result<(Response<'static>, flow::Transition)> {
-        self.mailbox.0.mailbox.force_sync().await?;
+        self.mailbox.internal.mailbox.force_sync().await?;
 
-        let updates = self.mailbox.update().await?;
+        let updates = self.mailbox.update(UpdateParameters::default()).await?;
         Ok((
             Response::build()
                 .to_req(self.req)
@@ -185,19 +208,39 @@ impl<'a> SelectedContext<'a> {
         kind: &StoreType,
         response: &StoreResponse,
         flags: &[Flag<'a>],
+        modifiers: &[StoreModifier],
         uid: &bool,
     ) -> Result<(Response<'static>, flow::Transition)> {
-        let data = self
+        let mut unchanged_since: Option<NonZeroU64> = None;
+        modifiers.iter().for_each(|m| match m {
+            StoreModifier::UnchangedSince(val) => {
+                unchanged_since = Some(*val);
+            },
+        });
+
+        let (data, modified) = self
             .mailbox
-            .store(sequence_set, kind, response, flags, uid)
+            .store(sequence_set, kind, response, flags, unchanged_since, uid)
             .await?;
 
-        Ok((
-            Response::build()
+        let mut ok_resp = Response::build()
                 .to_req(self.req)
                 .message("STORE completed")
-                .set_body(data)
-                .ok()?,
+                .set_body(data);
+
+
+        match modified[..] {
+            [] => (),
+            [_head, ..] => {
+                let modified_str = format!("MODIFIED {}", modified.into_iter().map(|x| x.to_string()).collect::<Vec<_>>().join(","));
+                ok_resp = ok_resp.code(Code::Other(CodeOther::unvalidated(modified_str.into_bytes())));
+            },
+        };
+
+
+        self.client_capabilities.store_modifiers_enable(modifiers);
+
+        Ok((ok_resp.ok()?,
             flow::Transition::None,
         ))
     }
diff --git a/src/imap/index.rs b/src/imap/index.rs
index 4853374..9b794b8 100644
--- a/src/imap/index.rs
+++ b/src/imap/index.rs
@@ -1,9 +1,9 @@
-use std::num::NonZeroU32;
+use std::num::{NonZeroU32, NonZeroU64};
 
 use anyhow::{anyhow, Result};
-use imap_codec::imap_types::sequence::{self, SeqOrUid, Sequence, SequenceSet};
+use imap_codec::imap_types::sequence::{SeqOrUid, Sequence, SequenceSet};
 
-use crate::mail::uidindex::{ImapUid, UidIndex};
+use crate::mail::uidindex::{ImapUid, ModSeq, UidIndex};
 use crate::mail::unique_ident::UniqueIdent;
 
 pub struct Index<'a> {
@@ -17,12 +17,10 @@ impl<'a> Index<'a> {
             .iter()
             .enumerate()
             .map(|(i_enum, (&uid, &uuid))| {
-                let flags = internal
+                let (_, modseq, flags) = internal
                     .table
                     .get(&uuid)
-                    .ok_or(anyhow!("mail is missing from index"))?
-                    .1
-                    .as_ref();
+                    .ok_or(anyhow!("mail is missing from index"))?;
                 let i_int: u32 = (i_enum + 1).try_into()?;
                 let i: NonZeroU32 = i_int.try_into()?;
 
@@ -30,6 +28,7 @@ impl<'a> Index<'a> {
                     i,
                     uid,
                     uuid,
+                    modseq: *modseq,
                     flags,
                 })
             })
@@ -61,10 +60,8 @@ impl<'a> Index<'a> {
         if self.imap_index.is_empty() {
             return vec![];
         }
-        let iter_strat = sequence::Strategy::Naive {
-            largest: self.last().expect("The mailbox is not empty").uid,
-        };
-        let mut unroll_seq = sequence_set.iter(iter_strat).collect::<Vec<_>>();
+        let largest = self.last().expect("The mailbox is not empty").uid;
+        let mut unroll_seq = sequence_set.iter(largest).collect::<Vec<_>>();
         unroll_seq.sort();
 
         let start_seq = match unroll_seq.iter().next() {
@@ -103,11 +100,9 @@ impl<'a> Index<'a> {
         if self.imap_index.is_empty() {
             return Ok(vec![]);
         }
-        let iter_strat = sequence::Strategy::Naive {
-            largest: NonZeroU32::try_from(self.imap_index.len() as u32)?,
-        };
+        let largest = NonZeroU32::try_from(self.imap_index.len() as u32)?;
         let mut acc = sequence_set
-            .iter(iter_strat)
+            .iter(largest)
             .map(|wanted_id| {
                 self.imap_index
                     .get((wanted_id.get() as usize) - 1)
@@ -131,6 +126,36 @@ impl<'a> Index<'a> {
             _ => self.fetch_on_id(sequence_set),
         }
     }
+
+    pub fn fetch_changed_since(
+        self: &'a Index<'a>,
+        sequence_set: &SequenceSet,
+        maybe_modseq: Option<NonZeroU64>,
+        by_uid: bool,
+    ) -> Result<Vec<&'a MailIndex<'a>>> {
+        let raw = self.fetch(sequence_set, by_uid)?;
+        let res = match maybe_modseq {
+            Some(pit) => raw.into_iter().filter(|midx| midx.modseq > pit).collect(),
+            None => raw,
+        };
+
+        Ok(res)
+    }
+
+    pub fn fetch_unchanged_since(
+        self: &'a Index<'a>,
+        sequence_set: &SequenceSet,
+        maybe_modseq: Option<NonZeroU64>,
+        by_uid: bool,
+    ) -> Result<(Vec<&'a MailIndex<'a>>, Vec<&'a MailIndex<'a>>)> {
+        let raw = self.fetch(sequence_set, by_uid)?;
+        let res = match maybe_modseq {
+            Some(pit) => raw.into_iter().partition(|midx| midx.modseq <= pit),
+            None => (raw, vec![]),
+        };
+
+        Ok(res)
+    }
 }
 
 #[derive(Clone, Debug)]
@@ -138,6 +163,7 @@ pub struct MailIndex<'a> {
     pub i: NonZeroU32,
     pub uid: ImapUid,
     pub uuid: UniqueIdent,
+    pub modseq: ModSeq,
     pub flags: &'a Vec<String>,
 }
 
diff --git a/src/imap/mail_view.rs b/src/imap/mail_view.rs
index eeb6b4b..a8db733 100644
--- a/src/imap/mail_view.rs
+++ b/src/imap/mail_view.rs
@@ -90,6 +90,7 @@ impl<'a> MailView<'a> {
                     Ok(body)
                 }
                 MessageDataItemName::InternalDate => self.internal_date(),
+                MessageDataItemName::ModSeq => Ok(self.modseq()),
             })
             .collect::<Result<Vec<_>, _>>()?;
 
@@ -252,6 +253,10 @@ impl<'a> MailView<'a> {
             .ok_or(anyhow!("Unable to parse internal date"))?;
         Ok(MessageDataItem::InternalDate(DateTime::unvalidated(dt)))
     }
+
+    fn modseq(&self) -> MessageDataItem<'static> {
+        MessageDataItem::ModSeq(self.in_idx.modseq)
+    }
 }
 
 pub enum SeenFlag {
diff --git a/src/imap/mailbox_view.rs b/src/imap/mailbox_view.rs
index 513567f..07fa3ad 100644
--- a/src/imap/mailbox_view.rs
+++ b/src/imap/mailbox_view.rs
@@ -1,21 +1,23 @@
-use std::num::NonZeroU32;
+use std::num::{NonZeroU32, NonZeroU64};
 use std::sync::Arc;
+use std::collections::HashSet;
 
 use anyhow::{anyhow, Error, Result};
 
 use futures::stream::{FuturesOrdered, StreamExt};
 
 use imap_codec::imap_types::core::Charset;
-use imap_codec::imap_types::fetch::{MacroOrMessageDataItemNames, MessageDataItem};
+use imap_codec::imap_types::fetch::MessageDataItem;
 use imap_codec::imap_types::flag::{Flag, FlagFetch, FlagPerm, StoreResponse, StoreType};
-use imap_codec::imap_types::response::{Code, Data, Status};
+use imap_codec::imap_types::response::{Code, CodeOther, Data, Status};
 use imap_codec::imap_types::search::SearchKey;
 use imap_codec::imap_types::sequence::SequenceSet;
 
+use crate::mail::unique_ident::UniqueIdent;
 use crate::mail::mailbox::Mailbox;
 use crate::mail::query::QueryScope;
 use crate::mail::snapshot::FrozenMailbox;
-use crate::mail::uidindex::{ImapUid, ImapUidvalidity};
+use crate::mail::uidindex::{ImapUid, ImapUidvalidity, ModSeq};
 
 use crate::imap::attributes::AttributesProxy;
 use crate::imap::flags;
@@ -32,6 +34,21 @@ const DEFAULT_FLAGS: [Flag; 5] = [
     Flag::Draft,
 ];
 
+pub struct UpdateParameters {
+    pub silence: HashSet<UniqueIdent>,
+    pub with_modseq: bool,
+    pub with_uid: bool,
+}
+impl Default for UpdateParameters {
+    fn default() -> Self {
+        Self {
+            silence: HashSet::new(),
+            with_modseq: false,
+            with_uid: false,
+        }
+    }
+}
+
 /// A MailboxView is responsible for giving the client the information
 /// it needs about a mailbox, such as an initial summary of the mailbox's
 /// content and continuous updates indicating when the content
@@ -39,12 +56,18 @@ const DEFAULT_FLAGS: [Flag; 5] = [
 /// To do this, it keeps a variable `known_state` that corresponds to
 /// what the client knows, and produces IMAP messages to be sent to the
 /// client that go along updates to `known_state`.
-pub struct MailboxView(pub FrozenMailbox);
+pub struct MailboxView {
+    pub internal: FrozenMailbox,
+    pub is_condstore: bool,
+}
 
 impl MailboxView {
     /// Creates a new IMAP view into a mailbox.
-    pub async fn new(mailbox: Arc<Mailbox>) -> Self {
-        Self(mailbox.frozen().await)
+    pub async fn new(mailbox: Arc<Mailbox>, is_cond: bool) -> Self {
+        Self { 
+            internal: mailbox.frozen().await,
+            is_condstore: is_cond,
+        }
     }
 
     /// Create an updated view, useful to make a diff
@@ -53,9 +76,9 @@ impl MailboxView {
     /// what the client knows and what is actually in the mailbox.
     /// This does NOT trigger a sync, it bases itself on what is currently
     /// loaded in RAM by Bayou.
-    pub async fn update(&mut self) -> Result<Vec<Body<'static>>> {
-        let old_snapshot = self.0.update().await;
-        let new_snapshot = &self.0.snapshot;
+    pub async fn update(&mut self, params: UpdateParameters) -> Result<Vec<Body<'static>>> {
+        let old_snapshot = self.internal.update().await;
+        let new_snapshot = &self.internal.snapshot;
 
         let mut data = Vec::<Body>::new();
 
@@ -99,19 +122,31 @@ impl MailboxView {
         } else {
             // - if flags changed for existing mails, tell client
             for (i, (_uid, uuid)) in new_snapshot.idx_by_uid.iter().enumerate() {
+                if params.silence.contains(uuid) {
+                    continue;
+                }
+
                 let old_mail = old_snapshot.table.get(uuid);
                 let new_mail = new_snapshot.table.get(uuid);
                 if old_mail.is_some() && old_mail != new_mail {
-                    if let Some((uid, flags)) = new_mail {
+                    if let Some((uid, modseq, flags)) = new_mail {
+                        let mut items = vec![
+                            MessageDataItem::Flags(
+                                flags.iter().filter_map(|f| flags::from_str(f)).collect(),
+                            ),
+                        ];
+
+                        if params.with_uid {
+                            items.push(MessageDataItem::Uid(*uid));
+                        }
+
+                        if params.with_modseq {
+                            items.push(MessageDataItem::ModSeq(*modseq));
+                        }
+
                         data.push(Body::Data(Data::Fetch {
                             seq: NonZeroU32::try_from((i + 1) as u32).unwrap(),
-                            items: vec![
-                                MessageDataItem::Uid(*uid),
-                                MessageDataItem::Flags(
-                                    flags.iter().filter_map(|f| flags::from_str(f)).collect(),
-                                ),
-                            ]
-                            .try_into()?,
+                            items: items.try_into()?,
                         }));
                     }
                 }
@@ -130,8 +165,11 @@ impl MailboxView {
         data.extend(self.flags_status()?.into_iter());
         data.push(self.uidvalidity_status()?);
         data.push(self.uidnext_status()?);
-        self.unseen_first_status()?
-            .map(|unseen_status| data.push(unseen_status));
+        if self.is_condstore {
+            data.push(self.highestmodseq_status()?);
+        }
+        /*self.unseen_first_status()?
+            .map(|unseen_status| data.push(unseen_status));*/
 
         Ok(data)
     }
@@ -140,50 +178,68 @@ impl MailboxView {
         &mut self,
         sequence_set: &SequenceSet,
         kind: &StoreType,
-        _response: &StoreResponse,
+        response: &StoreResponse,
         flags: &[Flag<'a>],
+        unchanged_since: Option<NonZeroU64>,
         is_uid_store: &bool,
-    ) -> Result<Vec<Body<'static>>> {
-        self.0.sync().await?;
+    ) -> Result<(Vec<Body<'static>>, Vec<NonZeroU32>)> {
+        self.internal.sync().await?;
 
         let flags = flags.iter().map(|x| x.to_string()).collect::<Vec<_>>();
 
         let idx = self.index()?;
-        let mails = idx.fetch(sequence_set, *is_uid_store)?;
-        for mi in mails.iter() {
+        let (editable, in_conflict) = idx
+            .fetch_unchanged_since(sequence_set, unchanged_since, *is_uid_store)?;
+
+        for mi in editable.iter() {
             match kind {
                 StoreType::Add => {
-                    self.0.mailbox.add_flags(mi.uuid, &flags[..]).await?;
+                    self.internal.mailbox.add_flags(mi.uuid, &flags[..]).await?;
                 }
                 StoreType::Remove => {
-                    self.0.mailbox.del_flags(mi.uuid, &flags[..]).await?;
+                    self.internal.mailbox.del_flags(mi.uuid, &flags[..]).await?;
                 }
                 StoreType::Replace => {
-                    self.0.mailbox.set_flags(mi.uuid, &flags[..]).await?;
+                    self.internal.mailbox.set_flags(mi.uuid, &flags[..]).await?;
                 }
             }
         }
 
-        // @TODO: handle _response
-        self.update().await
+        let silence = match response {
+            StoreResponse::Answer => HashSet::new(),
+            StoreResponse::Silent => editable.iter().map(|midx| midx.uuid).collect(),
+        };
+
+        let conflict_id_or_uid = match is_uid_store {
+            true => in_conflict.into_iter().map(|midx| midx.uid).collect(),
+            _ => in_conflict.into_iter().map(|midx| midx.i).collect(),
+        };
+
+        let summary = self.update(UpdateParameters {
+            with_uid: *is_uid_store,
+            with_modseq: unchanged_since.is_some(),
+            silence,
+        }).await?;
+
+        Ok((summary, conflict_id_or_uid))
     }
 
     pub async fn expunge(&mut self) -> Result<Vec<Body<'static>>> {
-        self.0.sync().await?;
-        let state = self.0.peek().await;
+        self.internal.sync().await?;
+        let state = self.internal.peek().await;
 
         let deleted_flag = Flag::Deleted.to_string();
         let msgs = state
             .table
             .iter()
-            .filter(|(_uuid, (_uid, flags))| flags.iter().any(|x| *x == deleted_flag))
+            .filter(|(_uuid, (_uid, _modseq, flags))| flags.iter().any(|x| *x == deleted_flag))
             .map(|(uuid, _)| *uuid);
 
         for msg in msgs {
-            self.0.mailbox.delete(msg).await?;
+            self.internal.mailbox.delete(msg).await?;
         }
 
-        self.update().await
+        self.update(UpdateParameters::default()).await
     }
 
     pub async fn copy(
@@ -197,7 +253,7 @@ impl MailboxView {
 
         let mut new_uuids = vec![];
         for mi in mails.iter() {
-            new_uuids.push(to.copy_from(&self.0.mailbox, mi.uuid).await?);
+            new_uuids.push(to.copy_from(&self.internal.mailbox, mi.uuid).await?);
         }
 
         let mut ret = vec![];
@@ -224,7 +280,7 @@ impl MailboxView {
         let mails = idx.fetch(sequence_set, *is_uid_copy)?;
 
         for mi in mails.iter() {
-            to.move_from(&self.0.mailbox, mi.uuid).await?;
+            to.move_from(&self.internal.mailbox, mi.uuid).await?;
         }
 
         let mut ret = vec![];
@@ -238,7 +294,10 @@ impl MailboxView {
             ret.push((mi.uid, dest_uid));
         }
 
-        let update = self.update().await?;
+        let update = self.update(UpdateParameters {
+            with_uid: *is_uid_copy,
+            ..UpdateParameters::default()
+        }).await?;
 
         Ok((to_state.uidvalidity, ret, update))
     }
@@ -248,27 +307,32 @@ impl MailboxView {
     pub async fn fetch<'b>(
         &self,
         sequence_set: &SequenceSet,
-        attributes: &'b MacroOrMessageDataItemNames<'static>,
+        ap: &AttributesProxy,
+        changed_since: Option<NonZeroU64>,
         is_uid_fetch: &bool,
     ) -> Result<Vec<Body<'static>>> {
         // [1/6] Pre-compute data
         //  a. what are the uuids of the emails we want?
         //  b. do we need to fetch the full body?
-        let ap = AttributesProxy::new(attributes, *is_uid_fetch);
+        //let ap = AttributesProxy::new(attributes, *is_uid_fetch);
         let query_scope = match ap.need_body() {
             true => QueryScope::Full,
             _ => QueryScope::Partial,
         };
         tracing::debug!("Query scope {:?}", query_scope);
         let idx = self.index()?;
-        let mail_idx_list = idx.fetch(sequence_set, *is_uid_fetch)?;
+        let mail_idx_list = idx.fetch_changed_since(
+            sequence_set, 
+            changed_since, 
+            *is_uid_fetch
+        )?;
 
         // [2/6] Fetch the emails
         let uuids = mail_idx_list
             .iter()
             .map(|midx| midx.uuid)
             .collect::<Vec<_>>();
-        let query_result = self.0.query(&uuids, query_scope).fetch().await?;
+        let query_result = self.internal.query(&uuids, query_scope).fetch().await?;
 
         // [3/6] Derive an IMAP-specific view from the results, apply the filters
         let views = query_result
@@ -294,7 +358,7 @@ impl MailboxView {
             .filter(|(_mv, seen)| matches!(seen, SeenFlag::MustAdd))
             .map(|(mv, _seen)| async move {
                 let seen_flag = Flag::Seen.to_string();
-                self.0
+                self.internal
                     .mailbox
                     .add_flags(*mv.query_result.uuid(), &[seen_flag])
                     .await?;
@@ -316,7 +380,7 @@ impl MailboxView {
         _charset: &Option<Charset<'a>>,
         search_key: &SearchKey<'a>,
         uid: bool,
-    ) -> Result<Vec<Body<'static>>> {
+    ) -> Result<(Vec<Body<'static>>, bool)> {
         // 1. Compute the subset of sequence identifiers we need to fetch
         // based on the search query
         let crit = search::Criteria(search_key);
@@ -332,20 +396,30 @@ impl MailboxView {
         // 4. Fetch additional info about the emails
         let query_scope = crit.query_scope();
         let uuids = to_fetch.iter().map(|midx| midx.uuid).collect::<Vec<_>>();
-        let query_result = self.0.query(&uuids, query_scope).fetch().await?;
+        let query_result = self.internal.query(&uuids, query_scope).fetch().await?;
 
         // 5. If needed, filter the selection based on the body
         let kept_query = crit.filter_on_query(&to_fetch, &query_result)?;
 
         // 6. Format the result according to the client's taste:
         // either return UID or ID.
-        let final_selection = kept_idx.into_iter().chain(kept_query.into_iter());
+        let final_selection = kept_idx.iter().chain(kept_query.iter());
         let selection_fmt = match uid {
             true => final_selection.map(|in_idx| in_idx.uid).collect(),
             _ => final_selection.map(|in_idx| in_idx.i).collect(),
         };
 
-        Ok(vec![Body::Data(Data::Search(selection_fmt))])
+        // 7. Add the modseq entry if needed
+        let is_modseq = crit.is_modseq();
+        let maybe_modseq = match is_modseq {
+            true => {
+                let final_selection = kept_idx.iter().chain(kept_query.iter());
+                final_selection.map(|in_idx| in_idx.modseq).max().map(|r| NonZeroU64::try_from(r)).transpose()?
+            },
+            _ => None,
+        };
+
+        Ok((vec![Body::Data(Data::Search(selection_fmt, maybe_modseq))], is_modseq))
     }
 
     // ----
@@ -354,7 +428,7 @@ impl MailboxView {
     /// It's not trivial to refactor the code to do that, so we are doing
     /// some useless computation for now...
     fn index<'a>(&'a self) -> Result<Index<'a>> {
-        Index::new(&self.0.snapshot)
+        Index::new(&self.internal.snapshot)
     }
 
     /// Produce an OK [UIDVALIDITY _] message corresponding to `known_state`
@@ -369,7 +443,7 @@ impl MailboxView {
     }
 
     pub(crate) fn uidvalidity(&self) -> ImapUidvalidity {
-        self.0.snapshot.uidvalidity
+        self.internal.snapshot.uidvalidity
     }
 
     /// Produce an OK [UIDNEXT _] message corresponding to `known_state`
@@ -384,7 +458,19 @@ impl MailboxView {
     }
 
     pub(crate) fn uidnext(&self) -> ImapUid {
-        self.0.snapshot.uidnext
+        self.internal.snapshot.uidnext
+    }
+
+    pub(crate) fn highestmodseq_status(&self) -> Result<Body<'static>> {
+        Ok(Body::Status(Status::ok(
+            None, 
+            Some(Code::Other(CodeOther::unvalidated(format!("HIGHESTMODSEQ {}", self.highestmodseq()).into_bytes()))),
+            "Highest",
+        )?))
+    }
+
+    pub(crate) fn highestmodseq(&self) -> ModSeq {
+        self.internal.snapshot.highestmodseq
     }
 
     /// Produce an EXISTS message corresponding to the number of mails
@@ -394,7 +480,7 @@ impl MailboxView {
     }
 
     pub(crate) fn exists(&self) -> Result<u32> {
-        Ok(u32::try_from(self.0.snapshot.idx_by_uid.len())?)
+        Ok(u32::try_from(self.internal.snapshot.idx_by_uid.len())?)
     }
 
     /// Produce a RECENT message corresponding to the number of
@@ -403,6 +489,7 @@ impl MailboxView {
         Ok(Body::Data(Data::Recent(self.recent()?)))
     }
 
+    #[allow(dead_code)]
     fn unseen_first_status(&self) -> Result<Option<Body<'static>>> {
         Ok(self
             .unseen_first()?
@@ -412,21 +499,22 @@ impl MailboxView {
             .transpose()?)
     }
 
+    #[allow(dead_code)]
     fn unseen_first(&self) -> Result<Option<NonZeroU32>> {
         Ok(self
-            .0
+            .internal
             .snapshot
             .table
             .values()
             .enumerate()
-            .find(|(_i, (_imap_uid, flags))| !flags.contains(&"\\Seen".to_string()))
+            .find(|(_i, (_imap_uid, _modseq, flags))| !flags.contains(&"\\Seen".to_string()))
             .map(|(i, _)| NonZeroU32::try_from(i as u32 + 1))
             .transpose()?)
     }
 
     pub(crate) fn recent(&self) -> Result<u32> {
         let recent = self
-            .0
+            .internal
             .snapshot
             .idx_by_flag
             .get(&"\\Recent".to_string())
@@ -443,7 +531,7 @@ impl MailboxView {
         // 1. Collecting all the possible flags in the mailbox
         // 1.a Fetch them from our index
         let mut known_flags: Vec<Flag> = self
-            .0
+            .internal
             .snapshot
             .idx_by_flag
             .flags()
@@ -483,9 +571,9 @@ impl MailboxView {
     }
 
     pub(crate) fn unseen_count(&self) -> usize {
-        let total = self.0.snapshot.table.len();
+        let total = self.internal.snapshot.table.len();
         let seen = self
-            .0
+            .internal
             .snapshot
             .idx_by_flag
             .get(&Flag::Seen.to_string())
@@ -524,6 +612,7 @@ mod tests {
                     peek: false,
                 },
             ]),
+            &[],
             false,
         );
 
@@ -535,12 +624,13 @@ mod tests {
             rfc822_size: 8usize,
         };
 
-        let index_entry = (NonZeroU32::MIN, vec![]);
+        let index_entry = (NonZeroU32::MIN, NonZeroU64::MIN, vec![]);
         let mail_in_idx = MailIndex {
             i: NonZeroU32::MIN,
             uid: index_entry.0,
+            modseq: index_entry.1,
             uuid: unique_ident::gen_ident(),
-            flags: &index_entry.1,
+            flags: &index_entry.2,
         };
         let rfc822 = b"Subject: hello\r\nFrom: a@a.a\r\nTo: b@b.b\r\nDate: Thu, 12 Oct 2023 08:45:28 +0000\r\n\r\nhello world";
         let qr = QueryResult::FullResult {
diff --git a/src/imap/mod.rs b/src/imap/mod.rs
index 2640183..61a265a 100644
--- a/src/imap/mod.rs
+++ b/src/imap/mod.rs
@@ -175,6 +175,11 @@ async fn client(mut ctx: ClientContext) -> Result<()> {
                         }
                     }
                 },
+                flow => {
+                    server.enqueue_status(Status::bye(None, "Unsupported server flow event").unwrap());
+                    tracing::error!("session task exited for {:?} due to unsupported flow {:?}", ctx.addr, flow);
+
+                }
             },
 
             // Managing response generated by Aerogramme
diff --git a/src/imap/search.rs b/src/imap/search.rs
index c4888d0..61cbad5 100644
--- a/src/imap/search.rs
+++ b/src/imap/search.rs
@@ -1,8 +1,8 @@
-use std::num::NonZeroU32;
+use std::num::{NonZeroU32, NonZeroU64};
 
 use anyhow::Result;
 use imap_codec::imap_types::core::NonEmptyVec;
-use imap_codec::imap_types::search::SearchKey;
+use imap_codec::imap_types::search::{SearchKey, MetadataItemSearch};
 use imap_codec::imap_types::sequence::{SeqOrUid, Sequence, SequenceSet};
 
 use crate::imap::index::MailIndex;
@@ -112,6 +112,17 @@ impl<'a> Criteria<'a> {
         }
     }
 
+    pub fn is_modseq(&self) -> bool {
+        use SearchKey::*;
+        match self.0 {
+            And(and_list) => and_list.as_ref().iter().any(|child| Criteria(child).is_modseq()),
+            Or(left, right) => Criteria(left).is_modseq() || Criteria(right).is_modseq(),
+            Not(child) => Criteria(child).is_modseq(),
+            ModSeq { .. } => true,
+            _ => false,
+        } 
+    }
+
     /// Returns emails that we now for sure we want to keep
     /// but also a second list of emails we need to investigate further by
     /// fetching some remote data
@@ -176,6 +187,7 @@ impl<'a> Criteria<'a> {
             // Sequence logic
             maybe_seq if is_sk_seq(maybe_seq) => is_keep_seq(maybe_seq, midx).into(),
             maybe_flag if is_sk_flag(maybe_flag) => is_keep_flag(maybe_flag, midx).into(),
+            ModSeq { metadata_item , modseq } => is_keep_modseq(metadata_item, modseq, midx).into(),
 
             // All the stuff we can't evaluate yet
             Bcc(_) | Cc(_) | From(_) | Header(..) | SentBefore(_) | SentOn(_) | SentSince(_)
@@ -210,9 +222,10 @@ impl<'a> Criteria<'a> {
             Not(expr) => !Criteria(expr).is_keep_on_query(mail_view),
             All => true,
 
-            // Reevaluating our previous logic...
+            //@FIXME Reevaluating our previous logic...
             maybe_seq if is_sk_seq(maybe_seq) => is_keep_seq(maybe_seq, &mail_view.in_idx),
             maybe_flag if is_sk_flag(maybe_flag) => is_keep_flag(maybe_flag, &mail_view.in_idx),
+            ModSeq { metadata_item , modseq } => is_keep_modseq(metadata_item, modseq, &mail_view.in_idx).into(),
 
             // Filter on mail meta
             Before(search_naive) => match mail_view.stored_naive_date() {
@@ -318,7 +331,8 @@ fn approx_sequence_set_size(seq_set: &SequenceSet) -> u64 {
 }
 
 // This is wrong as sequence UID can have holes,
-// as we don't know the number of messages in the mailbox also
+// as we don't know the number of messages in the mailbox also 
+// we gave to guess
 fn approx_sequence_size(seq: &Sequence) -> u64 {
     match seq {
         Sequence::Single(_) => 1,
@@ -458,3 +472,10 @@ fn is_keep_seq(sk: &SearchKey, midx: &MailIndex) -> bool {
         _ => unreachable!(),
     }
 }
+
+fn is_keep_modseq(filter: &Option<MetadataItemSearch>, modseq: &NonZeroU64, midx: &MailIndex) -> bool {
+    if filter.is_some() {
+        tracing::warn!(filter=?filter, "Ignoring search metadata filter as it's not supported yet");
+    }
+    modseq <= &midx.modseq 
+}
diff --git a/src/mail/mailbox.rs b/src/mail/mailbox.rs
index aab200b..5e95f32 100644
--- a/src/mail/mailbox.rs
+++ b/src/mail/mailbox.rs
@@ -113,7 +113,7 @@ impl Mailbox {
         msg: IMF<'a>,
         ident: Option<UniqueIdent>,
         flags: &[Flag],
-    ) -> Result<(ImapUidvalidity, ImapUid)> {
+    ) -> Result<(ImapUidvalidity, ImapUid, ModSeq)> {
         self.mbox.write().await.append(msg, ident, flags).await
     }
 
@@ -271,7 +271,7 @@ impl MailboxInternal {
         mail: IMF<'_>,
         ident: Option<UniqueIdent>,
         flags: &[Flag],
-    ) -> Result<(ImapUidvalidity, ImapUid)> {
+    ) -> Result<(ImapUidvalidity, ImapUid, ModSeq)> {
         let ident = ident.unwrap_or_else(gen_ident);
         let message_key = gen_key();
 
@@ -312,14 +312,14 @@ impl MailboxInternal {
         let add_mail_op = uid_state.op_mail_add(ident, flags.to_vec());
 
         let uidvalidity = uid_state.uidvalidity;
-        let uid = match add_mail_op {
-            UidIndexOp::MailAdd(_, uid, _) => uid,
+        let (uid, modseq) = match add_mail_op {
+            UidIndexOp::MailAdd(_, uid, modseq, _) => (uid, modseq),
             _ => unreachable!(),
         };
 
         self.uid_index.push(add_mail_op).await?;
 
-        Ok((uidvalidity, uid))
+        Ok((uidvalidity, uid, modseq))
     }
 
     async fn append_from_s3<'a>(
@@ -432,7 +432,7 @@ impl MailboxInternal {
             .table
             .get(&source_id)
             .ok_or(anyhow!("Source mail not found"))?
-            .1
+            .2
             .clone();
 
         futures::try_join!(
@@ -465,6 +465,9 @@ impl MailboxInternal {
     }
 }
 
+// Can be useful to debug so we want this code
+// to be available to developers
+#[allow(dead_code)]
 fn dump(uid_index: &Bayou<UidIndex>) {
     let s = uid_index.state();
     println!("---- MAILBOX STATE ----");
@@ -476,7 +479,7 @@ fn dump(uid_index: &Bayou<UidIndex>) {
             "{} {} {}",
             uid,
             hex::encode(ident.0),
-            s.table.get(ident).cloned().unwrap().1.join(", ")
+            s.table.get(ident).cloned().unwrap().2.join(", ")
         );
     }
     println!();
diff --git a/src/mail/query.rs b/src/mail/query.rs
index 0838800..a183c5a 100644
--- a/src/mail/query.rs
+++ b/src/mail/query.rs
@@ -125,13 +125,6 @@ impl QueryResult {
         }
     }
 
-    fn into_partial(self, metadata: MailMeta) -> Option<Self> {
-        match self {
-            Self::IndexResult { uuid } => Some(Self::PartialResult { uuid, metadata }),
-            _ => None,
-        }
-    }
-
     fn into_full(self, content: Vec<u8>) -> Option<Self> {
         match self {
             Self::PartialResult { uuid, metadata } => Some(Self::FullResult {
diff --git a/src/mail/uidindex.rs b/src/mail/uidindex.rs
index 01f8c9c..248aab1 100644
--- a/src/mail/uidindex.rs
+++ b/src/mail/uidindex.rs
@@ -1,4 +1,4 @@
-use std::num::NonZeroU32;
+use std::num::{NonZeroU32, NonZeroU64};
 
 use im::{HashMap, OrdMap, OrdSet};
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
@@ -6,10 +6,11 @@ use serde::{Deserialize, Deserializer, Serialize, Serializer};
 use crate::bayou::*;
 use crate::mail::unique_ident::UniqueIdent;
 
+pub type ModSeq = NonZeroU64;
 pub type ImapUid = NonZeroU32;
 pub type ImapUidvalidity = NonZeroU32;
 pub type Flag = String;
-pub type IndexEntry = (ImapUid, Vec<Flag>);
+pub type IndexEntry = (ImapUid, ModSeq, Vec<Flag>);
 
 /// A UidIndex handles the mutable part of a mailbox
 /// It is built by running the event log on it
@@ -23,28 +24,33 @@ pub struct UidIndex {
 
     // Indexes optimized for queries
     pub idx_by_uid: OrdMap<ImapUid, UniqueIdent>,
+    pub idx_by_modseq: OrdMap<ModSeq, UniqueIdent>,
     pub idx_by_flag: FlagIndex,
 
-    // Counters
+    // "Public" Counters
     pub uidvalidity: ImapUidvalidity,
     pub uidnext: ImapUid,
+    pub highestmodseq: ModSeq,
+
+    // "Internal" Counters
     pub internalseq: ImapUid,
+    pub internalmodseq: ModSeq,
 }
 
 #[derive(Clone, Serialize, Deserialize, Debug)]
 pub enum UidIndexOp {
-    MailAdd(UniqueIdent, ImapUid, Vec<Flag>),
+    MailAdd(UniqueIdent, ImapUid, ModSeq, Vec<Flag>),
     MailDel(UniqueIdent),
-    FlagAdd(UniqueIdent, Vec<Flag>),
-    FlagDel(UniqueIdent, Vec<Flag>),
-    FlagSet(UniqueIdent, Vec<Flag>),
+    FlagAdd(UniqueIdent, ModSeq, Vec<Flag>),
+    FlagDel(UniqueIdent, ModSeq, Vec<Flag>),
+    FlagSet(UniqueIdent, ModSeq, Vec<Flag>),
     BumpUidvalidity(u32),
 }
 
 impl UidIndex {
     #[must_use]
     pub fn op_mail_add(&self, ident: UniqueIdent, flags: Vec<Flag>) -> UidIndexOp {
-        UidIndexOp::MailAdd(ident, self.internalseq, flags)
+        UidIndexOp::MailAdd(ident, self.internalseq, self.internalmodseq, flags)
     }
 
     #[must_use]
@@ -54,17 +60,17 @@ impl UidIndex {
 
     #[must_use]
     pub fn op_flag_add(&self, ident: UniqueIdent, flags: Vec<Flag>) -> UidIndexOp {
-        UidIndexOp::FlagAdd(ident, flags)
+        UidIndexOp::FlagAdd(ident, self.internalmodseq, flags)
     }
 
     #[must_use]
     pub fn op_flag_del(&self, ident: UniqueIdent, flags: Vec<Flag>) -> UidIndexOp {
-        UidIndexOp::FlagDel(ident, flags)
+        UidIndexOp::FlagDel(ident, self.internalmodseq, flags)
     }
 
     #[must_use]
     pub fn op_flag_set(&self, ident: UniqueIdent, flags: Vec<Flag>) -> UidIndexOp {
-        UidIndexOp::FlagSet(ident, flags)
+        UidIndexOp::FlagSet(ident, self.internalmodseq, flags)
     }
 
     #[must_use]
@@ -74,18 +80,19 @@ impl UidIndex {
 
     // INTERNAL functions to keep state consistent
 
-    fn reg_email(&mut self, ident: UniqueIdent, uid: ImapUid, flags: &[Flag]) {
+    fn reg_email(&mut self, ident: UniqueIdent, uid: ImapUid, modseq: ModSeq, flags: &[Flag]) {
         // Insert the email in our table
-        self.table.insert(ident, (uid, flags.to_owned()));
+        self.table.insert(ident, (uid, modseq, flags.to_owned()));
 
         // Update the indexes/caches
         self.idx_by_uid.insert(uid, ident);
         self.idx_by_flag.insert(uid, flags);
+        self.idx_by_modseq.insert(modseq, ident);
     }
 
     fn unreg_email(&mut self, ident: &UniqueIdent) {
         // We do nothing if the mail does not exist
-        let (uid, flags) = match self.table.get(ident) {
+        let (uid, modseq, flags) = match self.table.get(ident) {
             Some(v) => v,
             None => return,
         };
@@ -93,6 +100,7 @@ impl UidIndex {
         // Delete all cache entries
         self.idx_by_uid.remove(uid);
         self.idx_by_flag.remove(*uid, flags);
+        self.idx_by_modseq.remove(modseq);
 
         // Remove from source of trust
         self.table.remove(ident);
@@ -103,11 +111,17 @@ impl Default for UidIndex {
     fn default() -> Self {
         Self {
             table: OrdMap::new(),
+
             idx_by_uid: OrdMap::new(),
+            idx_by_modseq: OrdMap::new(),
             idx_by_flag: FlagIndex::new(),
+
             uidvalidity: NonZeroU32::new(1).unwrap(),
             uidnext: NonZeroU32::new(1).unwrap(),
+            highestmodseq: NonZeroU64::new(1).unwrap(),
+
             internalseq: NonZeroU32::new(1).unwrap(),
+            internalmodseq: NonZeroU64::new(1).unwrap(),
         }
     }
 }
@@ -118,17 +132,24 @@ impl BayouState for UidIndex {
     fn apply(&self, op: &UidIndexOp) -> Self {
         let mut new = self.clone();
         match op {
-            UidIndexOp::MailAdd(ident, uid, flags) => {
-                // Change UIDValidity if there is a conflict
-                if *uid < new.internalseq {
+            UidIndexOp::MailAdd(ident, uid, modseq, flags) => {
+                // Change UIDValidity if there is a UID conflict or a MODSEQ conflict
+                // @FIXME Need to prove that summing work
+                // The intuition: we increase the UIDValidity by the number of possible conflicts
+                if *uid < new.internalseq || *modseq < new.internalmodseq {
+                    let bump_uid = new.internalseq.get() - uid.get();
+                    let bump_modseq = (new.internalmodseq.get() - modseq.get()) as u32;
                     new.uidvalidity =
-                        NonZeroU32::new(new.uidvalidity.get() + new.internalseq.get() - uid.get())
+                        NonZeroU32::new(new.uidvalidity.get() + bump_uid + bump_modseq)
                             .unwrap();
                 }
 
                 // Assign the real uid of the email
                 let new_uid = new.internalseq;
 
+                // Assign the real modseq of the email and its new flags
+                let new_modseq = new.internalmodseq;
+
                 // Delete the previous entry if any.
                 // Our proof has no assumption on `ident` uniqueness,
                 // so we must handle this case even it is very unlikely
@@ -137,10 +158,14 @@ impl BayouState for UidIndex {
                 new.unreg_email(ident);
 
                 // We record our email and update ou caches
-                new.reg_email(*ident, new_uid, flags);
+                new.reg_email(*ident, new_uid, new_modseq, flags);
 
                 // Update counters
+                new.highestmodseq = new.internalmodseq;
+
                 new.internalseq = NonZeroU32::new(new.internalseq.get() + 1).unwrap();
+                new.internalmodseq = NonZeroU64::new(new.internalmodseq.get() + 1).unwrap();
+
                 new.uidnext = new.internalseq;
             }
             UidIndexOp::MailDel(ident) => {
@@ -150,8 +175,16 @@ impl BayouState for UidIndex {
                 // We update the counter
                 new.internalseq = NonZeroU32::new(new.internalseq.get() + 1).unwrap();
             }
-            UidIndexOp::FlagAdd(ident, new_flags) => {
-                if let Some((uid, existing_flags)) = new.table.get_mut(ident) {
+            UidIndexOp::FlagAdd(ident, candidate_modseq, new_flags) => {
+                if let Some((uid, email_modseq, existing_flags)) = new.table.get_mut(ident) {
+                    // Bump UIDValidity if required
+                    if *candidate_modseq < new.internalmodseq {
+                        let bump_modseq = (new.internalmodseq.get() - candidate_modseq.get()) as u32;
+                        new.uidvalidity =
+                            NonZeroU32::new(new.uidvalidity.get() + bump_modseq)
+                                .unwrap();
+                    }
+
                     // Add flags to the source of trust and the cache
                     let mut to_add: Vec<Flag> = new_flags
                         .iter()
@@ -159,18 +192,48 @@ impl BayouState for UidIndex {
                         .cloned()
                         .collect();
                     new.idx_by_flag.insert(*uid, &to_add);
+                    *email_modseq = new.internalmodseq;
+                    new.idx_by_modseq.insert(new.internalmodseq, *ident);
                     existing_flags.append(&mut to_add);
+
+                    // Update counters
+                    new.highestmodseq = new.internalmodseq;
+                    new.internalmodseq = NonZeroU64::new(new.internalmodseq.get() + 1).unwrap();
                 }
             }
-            UidIndexOp::FlagDel(ident, rm_flags) => {
-                if let Some((uid, existing_flags)) = new.table.get_mut(ident) {
+            UidIndexOp::FlagDel(ident, candidate_modseq, rm_flags) => {
+                if let Some((uid, email_modseq, existing_flags)) = new.table.get_mut(ident) {
+                    // Bump UIDValidity if required
+                    if *candidate_modseq < new.internalmodseq {
+                        let bump_modseq = (new.internalmodseq.get() - candidate_modseq.get()) as u32;
+                        new.uidvalidity =
+                            NonZeroU32::new(new.uidvalidity.get() + bump_modseq)
+                                .unwrap();
+                    }
+
                     // Remove flags from the source of trust and the cache
                     existing_flags.retain(|x| !rm_flags.contains(x));
                     new.idx_by_flag.remove(*uid, rm_flags);
+
+                    // Register that email has been modified
+                    new.idx_by_modseq.insert(new.internalmodseq, *ident);
+                    *email_modseq = new.internalmodseq;
+
+                    // Update counters
+                    new.highestmodseq = new.internalmodseq;
+                    new.internalmodseq = NonZeroU64::new(new.internalmodseq.get() + 1).unwrap();
                 }
             }
-            UidIndexOp::FlagSet(ident, new_flags) => {
-                if let Some((uid, existing_flags)) = new.table.get_mut(ident) {
+            UidIndexOp::FlagSet(ident, candidate_modseq, new_flags) => {
+                if let Some((uid, email_modseq, existing_flags)) = new.table.get_mut(ident) {
+                    // Bump UIDValidity if required
+                    if *candidate_modseq < new.internalmodseq {
+                        let bump_modseq = (new.internalmodseq.get() - candidate_modseq.get()) as u32;
+                        new.uidvalidity =
+                            NonZeroU32::new(new.uidvalidity.get() + bump_modseq)
+                                .unwrap();
+                    }
+
                     // Remove flags from the source of trust and the cache
                     let (keep_flags, rm_flags): (Vec<String>, Vec<String>) = existing_flags
                         .iter()
@@ -185,6 +248,14 @@ impl BayouState for UidIndex {
                     existing_flags.append(&mut to_add);
                     new.idx_by_flag.remove(*uid, &rm_flags);
                     new.idx_by_flag.insert(*uid, &to_add);
+                    
+                    // Register that email has been modified
+                    new.idx_by_modseq.insert(new.internalmodseq, *ident);
+                    *email_modseq = new.internalmodseq;
+
+                    // Update counters
+                    new.highestmodseq = new.internalmodseq;
+                    new.internalmodseq = NonZeroU64::new(new.internalmodseq.get() + 1).unwrap();
                 }
             }
             UidIndexOp::BumpUidvalidity(count) => {
@@ -238,10 +309,14 @@ impl FlagIndex {
 
 #[derive(Serialize, Deserialize)]
 struct UidIndexSerializedRepr {
-    mails: Vec<(ImapUid, UniqueIdent, Vec<Flag>)>,
+    mails: Vec<(ImapUid, ModSeq, UniqueIdent, Vec<Flag>)>,
+
     uidvalidity: ImapUidvalidity,
     uidnext: ImapUid,
+    highestmodseq: ModSeq,
+
     internalseq: ImapUid,
+    internalmodseq: ModSeq,
 }
 
 impl<'de> Deserialize<'de> for UidIndex {
@@ -253,16 +328,22 @@ impl<'de> Deserialize<'de> for UidIndex {
 
         let mut uidindex = UidIndex {
             table: OrdMap::new(),
+
             idx_by_uid: OrdMap::new(),
+            idx_by_modseq: OrdMap::new(),
             idx_by_flag: FlagIndex::new(),
+
             uidvalidity: val.uidvalidity,
             uidnext: val.uidnext,
+            highestmodseq: val.highestmodseq,
+
             internalseq: val.internalseq,
+            internalmodseq: val.internalmodseq,
         };
 
         val.mails
             .iter()
-            .for_each(|(u, i, f)| uidindex.reg_email(*i, *u, f));
+            .for_each(|(uid, modseq, uuid, flags)| uidindex.reg_email(*uuid, *uid, *modseq, flags));
 
         Ok(uidindex)
     }
@@ -274,15 +355,17 @@ impl Serialize for UidIndex {
         S: Serializer,
     {
         let mut mails = vec![];
-        for (ident, (uid, flags)) in self.table.iter() {
-            mails.push((*uid, *ident, flags.clone()));
+        for (ident, (uid, modseq, flags)) in self.table.iter() {
+            mails.push((*uid, *modseq, *ident, flags.clone()));
         }
 
         let val = UidIndexSerializedRepr {
             mails,
             uidvalidity: self.uidvalidity,
             uidnext: self.uidnext,
+            highestmodseq: self.highestmodseq,
             internalseq: self.internalseq,
+            internalmodseq: self.internalmodseq,
         };
 
         val.serialize(serializer)
@@ -308,8 +391,9 @@ mod tests {
 
             // Early checks
             assert_eq!(state.table.len(), 1);
-            let (uid, flags) = state.table.get(&m).unwrap();
+            let (uid, modseq, flags) = state.table.get(&m).unwrap();
             assert_eq!(*uid, NonZeroU32::new(1).unwrap());
+            assert_eq!(*modseq, NonZeroU64::new(1).unwrap());
             assert_eq!(flags.len(), 2);
             let ident = state.idx_by_uid.get(&NonZeroU32::new(1).unwrap()).unwrap();
             assert_eq!(&m, ident);
@@ -364,7 +448,7 @@ mod tests {
         {
             let m = UniqueIdent([0x03; 24]);
             let f = vec!["\\Archive".to_string(), "\\Recent".to_string()];
-            let ev = UidIndexOp::MailAdd(m, NonZeroU32::new(1).unwrap(), f);
+            let ev = UidIndexOp::MailAdd(m, NonZeroU32::new(1).unwrap(), NonZeroU64::new(1).unwrap(), f);
             state = state.apply(&ev);
         }
 
diff --git a/tests/behavior.rs b/tests/behavior.rs
index 17f3a72..205f5e1 100644
--- a/tests/behavior.rs
+++ b/tests/behavior.rs
@@ -2,6 +2,7 @@ use anyhow::Context;
 
 mod common;
 use crate::common::fragments::*;
+use crate::common::constants::*;
 
 fn main() {
     rfc3501_imap4rev1_base();
@@ -9,10 +10,12 @@ fn main() {
     rfc5161_imapext_enable();
     rfc6851_imapext_move();
     rfc7888_imapext_literal();
+    rfc4551_imapext_condstore();
+    println!("✅ SUCCESS 🌟🚀🥳🙏🥹");
 }
 
 fn rfc3501_imap4rev1_base() {
-    println!("rfc3501_imap4rev1_base");
+    println!("🧪 rfc3501_imap4rev1_base");
     common::aerogramme_provider_daemon_dev(|imap_socket, lmtp_socket| {
         connect(imap_socket).context("server says hello")?;
         capability(imap_socket, Extension::None).context("check server capabilities")?;
@@ -20,20 +23,26 @@ fn rfc3501_imap4rev1_base() {
         create_mailbox(imap_socket, Mailbox::Archive).context("created mailbox archive")?;
         // UNSUBSCRIBE IS NOT IMPLEMENTED YET
         //unsubscribe_mailbox(imap_socket).context("unsubscribe from archive")?;
-        select(imap_socket, Mailbox::Inbox, None).context("select inbox")?;
+        let select_res = select(imap_socket, Mailbox::Inbox, SelectMod::None).context("select inbox")?;
+        assert!(select_res.contains("* 0 EXISTS"));
+
         check(imap_socket).context("check must run")?;
-        status_mailbox(imap_socket, Mailbox::Archive).context("status of archive from inbox")?;
+        status(imap_socket, Mailbox::Archive, StatusKind::UidNext).context("status of archive from inbox")?;
         lmtp_handshake(lmtp_socket).context("handshake lmtp done")?;
         lmtp_deliver_email(lmtp_socket, Email::Multipart).context("mail delivered successfully")?;
-        noop_exists(imap_socket).context("noop loop must detect a new email")?;
-        fetch_rfc822(imap_socket, Selection::FirstId, Email::Multipart)
+        noop_exists(imap_socket, 1).context("noop loop must detect a new email")?;
+
+        let srv_msg = fetch(imap_socket, Selection::FirstId, FetchKind::Rfc822, FetchMod::None)
             .context("fetch rfc822 message, should be our first message")?;
+        let orig_email = std::str::from_utf8(EMAIL1)?;
+        assert!(srv_msg.contains(orig_email));
+        
         copy(imap_socket, Selection::FirstId, Mailbox::Archive)
             .context("copy message to the archive mailbox")?;
         append_email(imap_socket, Email::Basic).context("insert email in INBOX")?;
-        // SEARCH IS NOT IMPLEMENTED YET
-        //search(imap_socket).expect("search should return something");
-        add_flags_email(imap_socket, Selection::FirstId, Flag::Deleted)
+        noop_exists(imap_socket, 2).context("noop loop must detect a new email")?;
+        search(imap_socket, SearchKind::Text("OoOoO")).expect("search should return something");
+        store(imap_socket, Selection::FirstId, Flag::Deleted, StoreAction::AddFlags, StoreMod::None)
             .context("should add delete flag to the email")?;
         expunge(imap_socket).context("expunge emails")?;
         rename_mailbox(imap_socket, Mailbox::Archive, Mailbox::Drafts)
@@ -45,7 +54,7 @@ fn rfc3501_imap4rev1_base() {
 }
 
 fn rfc3691_imapext_unselect() {
-    println!("rfc3691_imapext_unselect");
+    println!("🧪 rfc3691_imapext_unselect");
     common::aerogramme_provider_daemon_dev(|imap_socket, lmtp_socket| {
         connect(imap_socket).context("server says hello")?;
 
@@ -54,18 +63,26 @@ fn rfc3691_imapext_unselect() {
 
         capability(imap_socket, Extension::Unselect).context("check server capabilities")?;
         login(imap_socket, Account::Alice).context("login test")?;
-        select(imap_socket, Mailbox::Inbox, None).context("select inbox")?;
-        noop_exists(imap_socket).context("noop loop must detect a new email")?;
-        add_flags_email(imap_socket, Selection::FirstId, Flag::Deleted)
+        let select_res = select(imap_socket, Mailbox::Inbox, SelectMod::None).context("select inbox")?;
+        assert!(select_res.contains("* 0 EXISTS"));
+
+        noop_exists(imap_socket, 1).context("noop loop must detect a new email")?;
+        store(imap_socket, Selection::FirstId, Flag::Deleted, StoreAction::AddFlags, StoreMod::None)
             .context("add delete flags to the email")?;
         unselect(imap_socket)
             .context("unselect inbox while preserving email with the \\Delete flag")?;
-        select(imap_socket, Mailbox::Inbox, Some(1)).context("select inbox again")?;
-        fetch_rfc822(imap_socket, Selection::FirstId, Email::Basic)
+        let select_res = select(imap_socket, Mailbox::Inbox, SelectMod::None).context("select inbox again")?;
+        assert!(select_res.contains("* 1 EXISTS"));
+
+        let srv_msg = fetch(imap_socket, Selection::FirstId, FetchKind::Rfc822, FetchMod::None)
             .context("message is still present")?;
+        let orig_email = std::str::from_utf8(EMAIL2)?;
+        assert!(srv_msg.contains(orig_email));
+
         close(imap_socket).context("close inbox and expunge message")?;
-        select(imap_socket, Mailbox::Inbox, Some(0))
+        let select_res = select(imap_socket, Mailbox::Inbox, SelectMod::None)
             .context("select inbox again and check it's empty")?;
+        assert!(select_res.contains("* 0 EXISTS"));
 
         Ok(())
     })
@@ -73,7 +90,7 @@ fn rfc3691_imapext_unselect() {
 }
 
 fn rfc5161_imapext_enable() {
-    println!("rfc5161_imapext_enable");
+    println!("🧪 rfc5161_imapext_enable");
     common::aerogramme_provider_daemon_dev(|imap_socket, _lmtp_socket| {
         connect(imap_socket).context("server says hello")?;
         login(imap_socket, Account::Alice).context("login test")?;
@@ -87,26 +104,37 @@ fn rfc5161_imapext_enable() {
 }
 
 fn rfc6851_imapext_move() {
-    println!("rfc6851_imapext_move");
+    println!("🧪 rfc6851_imapext_move");
     common::aerogramme_provider_daemon_dev(|imap_socket, lmtp_socket| {
         connect(imap_socket).context("server says hello")?;
 
         capability(imap_socket, Extension::Move).context("check server capabilities")?;
         login(imap_socket, Account::Alice).context("login test")?;
         create_mailbox(imap_socket, Mailbox::Archive).context("created mailbox archive")?;
-        select(imap_socket, Mailbox::Inbox, None).context("select inbox")?;
+        let select_res = select(imap_socket, Mailbox::Inbox, SelectMod::None).context("select inbox")?;
+        assert!(select_res.contains("* 0 EXISTS"));
 
         lmtp_handshake(lmtp_socket).context("handshake lmtp done")?;
         lmtp_deliver_email(lmtp_socket, Email::Basic).context("mail delivered successfully")?;
 
-        noop_exists(imap_socket).context("noop loop must detect a new email")?;
+        noop_exists(imap_socket, 1).context("noop loop must detect a new email")?;
         r#move(imap_socket, Selection::FirstId, Mailbox::Archive)
             .context("message from inbox moved to archive")?;
 
         unselect(imap_socket)
             .context("unselect inbox while preserving email with the \\Delete flag")?;
-        select(imap_socket, Mailbox::Archive, Some(1)).context("select archive")?;
-        fetch_rfc822(imap_socket, Selection::FirstId, Email::Basic).context("check mail exists")?;
+        let select_res = select(imap_socket, Mailbox::Archive, SelectMod::None).context("select archive")?;
+        assert!(select_res.contains("* 1 EXISTS"));
+
+        let srv_msg = fetch(
+            imap_socket, 
+            Selection::FirstId, 
+            FetchKind::Rfc822, 
+            FetchMod::None,
+        ).context("check mail exists")?;
+        let orig_email = std::str::from_utf8(EMAIL2)?;
+        assert!(srv_msg.contains(orig_email));
+
         logout(imap_socket).context("must quit")?;
 
         Ok(())
@@ -115,7 +143,7 @@ fn rfc6851_imapext_move() {
 }
 
 fn rfc7888_imapext_literal() {
-    println!("rfc7888_imapext_literal");
+    println!("🧪 rfc7888_imapext_literal");
     common::aerogramme_provider_daemon_dev(|imap_socket, _lmtp_socket| {
         connect(imap_socket).context("server says hello")?;
 
@@ -126,3 +154,49 @@ fn rfc7888_imapext_literal() {
     })
     .expect("test fully run");
 }
+
+fn rfc4551_imapext_condstore() {
+    println!("🧪 rfc4551_imapext_condstore");
+    common::aerogramme_provider_daemon_dev(|imap_socket, lmtp_socket| {
+        // Setup the test
+        connect(imap_socket).context("server says hello")?;
+
+        // RFC 3.1.1 Advertising Support for CONDSTORE
+        capability(imap_socket, Extension::Condstore).context("check server capabilities")?;
+        login(imap_socket, Account::Alice).context("login test")?;
+
+        // RFC 3.1.8.  CONDSTORE Parameter to SELECT and EXAMINE
+        let select_res = select(imap_socket, Mailbox::Inbox, SelectMod::Condstore).context("select inbox")?;
+        // RFC 3.1.2   New OK Untagged Responses for SELECT and EXAMINE
+        assert!(select_res.contains("[HIGHESTMODSEQ 1]"));
+
+        // RFC 3.1.3.  STORE and UID STORE Commands
+        lmtp_handshake(lmtp_socket).context("handshake lmtp done")?;
+        lmtp_deliver_email(lmtp_socket, Email::Basic).context("mail delivered successfully")?;
+        lmtp_deliver_email(lmtp_socket, Email::Multipart).context("mail delivered successfully")?;
+        noop_exists(imap_socket, 2).context("noop loop must detect a new email")?;
+        let store_res = store(imap_socket, Selection::All, Flag::Important, StoreAction::AddFlags, StoreMod::UnchangedSince(1))?;
+        assert!(store_res.contains("[MODIFIED 2]"));
+        assert!(store_res.contains("* 1 FETCH (FLAGS (\\Important) MODSEQ (3))"));
+        assert!(!store_res.contains("* 2 FETCH"));
+        assert_eq!(store_res.lines().count(), 2);
+
+        // RFC 3.1.4.  FETCH and UID FETCH Commands
+        let fetch_res = fetch(imap_socket, Selection::All, FetchKind::Rfc822Size, FetchMod::ChangedSince(2))?;
+        assert!(fetch_res.contains("* 1 FETCH (RFC822.SIZE 84 MODSEQ (3))"));
+        assert!(!fetch_res.contains("* 2 FETCH"));
+        assert_eq!(store_res.lines().count(), 2);
+
+        // RFC 3.1.5.  MODSEQ Search Criterion in SEARCH
+        let search_res = search(imap_socket, SearchKind::ModSeq(3))?;
+        // RFC 3.1.6.  Modified SEARCH Untagged Response
+        assert!(search_res.contains("* SEARCH 1 (MODSEQ 3)"));
+
+        // RFC 3.1.7   HIGHESTMODSEQ Status Data Items
+        let status_res = status(imap_socket, Mailbox::Inbox, StatusKind::HighestModSeq)?;
+        assert!(status_res.contains("HIGHESTMODSEQ 3"));
+
+        Ok(())
+    })
+    .expect("test fully run");
+}
diff --git a/tests/common/fragments.rs b/tests/common/fragments.rs
index 2e2fbd4..f9ad87e 100644
--- a/tests/common/fragments.rs
+++ b/tests/common/fragments.rs
@@ -34,7 +34,7 @@ pub enum Extension {
     None,
     Unselect,
     Move,
-    CondStore,
+    Condstore,
     LiteralPlus,
 }
 
@@ -63,6 +63,46 @@ pub enum Email {
 pub enum Selection {
     FirstId,
     SecondId,
+    All,
+}
+
+pub enum SelectMod {
+    None,
+    Condstore,
+}
+
+pub enum StoreAction {
+    AddFlags,
+    DelFlags,
+    SetFlags,
+    AddFlagsSilent,
+    DelFlagsSilent,
+    SetFlagsSilent,
+}
+
+pub enum StoreMod {
+    None,
+    UnchangedSince(u64),
+}
+
+pub enum FetchKind {
+    Rfc822,
+    Rfc822Size,
+}
+
+pub enum FetchMod {
+    None,
+    ChangedSince(u64),
+}
+
+pub enum SearchKind<'a> {
+    Text(&'a str),
+    ModSeq(u64),
+}
+
+pub enum StatusKind {
+    UidNext,
+    HighestModSeq,
 }
 
 pub fn capability(imap: &mut TcpStream, ext: Extension) -> Result<()> {
@@ -72,7 +112,7 @@ pub fn capability(imap: &mut TcpStream, ext: Extension) -> Result<()> {
         Extension::None => None,
         Extension::Unselect => Some("UNSELECT"),
         Extension::Move => Some("MOVE"),
-        Extension::CondStore => Some("CONDSTORE"),
+        Extension::Condstore => Some("CONDSTORE"),
         Extension::LiteralPlus => Some("LITERAL+"),
     };
 
@@ -125,7 +165,7 @@ pub fn create_mailbox(imap: &mut TcpStream, mbx: Mailbox) -> Result<()> {
     Ok(())
 }
 
-pub fn select(imap: &mut TcpStream, mbx: Mailbox, maybe_exists: Option<u64>) -> Result<()> {
+pub fn select(imap: &mut TcpStream, mbx: Mailbox, modifier: SelectMod) -> Result<String> {
     let mut buffer: [u8; 6000] = [0; 6000];
 
     let mbx_str = match mbx {
@@ -133,16 +173,18 @@ pub fn select(imap: &mut TcpStream, mbx: Mailbox, maybe_exists: Option<u64>) ->
         Mailbox::Archive => "Archive",
         Mailbox::Drafts => "Drafts",
     };
-    imap.write(format!("20 select {}\r\n", mbx_str).as_bytes())?;
+
+    let mod_str = match modifier {
+        SelectMod::Condstore => " (CONDSTORE)",
+        SelectMod::None => "",
+    };
+
+    imap.write(format!("20 select {}{}\r\n", mbx_str, mod_str).as_bytes())?;
 
     let read = read_lines(imap, &mut buffer, Some(&b"20 OK"[..]))?;
     let srv_msg = std::str::from_utf8(read)?;
-    if let Some(exists) = maybe_exists {
-        let expected = format!("* {} EXISTS", exists);
-        assert!(srv_msg.contains(&expected));
-    }
 
-    Ok(())
+    Ok(srv_msg.to_string())
 }
 
 pub fn unselect(imap: &mut TcpStream) -> Result<()> {
@@ -162,13 +204,22 @@ pub fn check(imap: &mut TcpStream) -> Result<()> {
     Ok(())
 }
 
-pub fn status_mailbox(imap: &mut TcpStream, mbx: Mailbox) -> Result<()> {
-    assert!(matches!(mbx, Mailbox::Archive));
-    imap.write(&b"25 STATUS Archive (UIDNEXT MESSAGES)\r\n"[..])?;
+pub fn status(imap: &mut TcpStream, mbx: Mailbox, sk: StatusKind) -> Result<String> {
+    let mbx_str = match mbx {
+        Mailbox::Inbox => "INBOX",
+        Mailbox::Archive => "Archive",
+        Mailbox::Drafts => "Drafts",
+    };
+    let sk_str = match sk {
+        StatusKind::UidNext => "(UIDNEXT)",
+        StatusKind::HighestModSeq => "(HIGHESTMODSEQ)",
+    };
+    imap.write(format!("25 STATUS {} {}\r\n", mbx_str, sk_str).as_bytes())?;
     let mut buffer: [u8; 6000] = [0; 6000];
-    let _read = read_lines(imap, &mut buffer, Some(&b"25 OK"[..]))?;
+    let read = read_lines(imap, &mut buffer, Some(&b"25 OK"[..]))?;
+    let srv_msg = std::str::from_utf8(read)?;
 
-    Ok(())
+    Ok(srv_msg.to_string())
 }
 
 pub fn lmtp_handshake(lmtp: &mut TcpStream) -> Result<()> {
@@ -206,7 +257,7 @@ pub fn lmtp_deliver_email(lmtp: &mut TcpStream, email_type: Email) -> Result<()>
     Ok(())
 }
 
-pub fn noop_exists(imap: &mut TcpStream) -> Result<()> {
+pub fn noop_exists(imap: &mut TcpStream, must_exists: u32) -> Result<()> {
     let mut buffer: [u8; 6000] = [0; 6000];
 
     let mut max_retry = 20;
@@ -216,35 +267,50 @@ pub fn noop_exists(imap: &mut TcpStream) -> Result<()> {
         let read = read_lines(imap, &mut buffer, Some(&b"30 OK"[..]))?;
         let srv_msg = std::str::from_utf8(read)?;
 
-        match (max_retry, srv_msg.lines().count()) {
-            (_, cnt) if cnt > 1 => break,
-            (0, _) => bail!("no more retry"),
-            _ => (),
+        for line in srv_msg.lines() {
+            if line.contains("EXISTS") {
+                let got = read_first_u32(line)?;
+                if got == must_exists {
+                    // Done
+                    return Ok(());
+                }
+            }
+        }
+
+        if max_retry <= 0 {
+            // Failed
+            bail!("no more retry");
         }
 
         thread::sleep(SMALL_DELAY);
     }
-
-    Ok(())
 }
 
-pub fn fetch_rfc822(imap: &mut TcpStream, selection: Selection, r#ref: Email) -> Result<()> {
+pub fn fetch(imap: &mut TcpStream, selection: Selection, kind: FetchKind, modifier: FetchMod) -> Result<String> {
     let mut buffer: [u8; 65535] = [0; 65535];
 
-    assert!(matches!(selection, Selection::FirstId));
-    imap.write(&b"40 fetch 1 rfc822\r\n"[..])?;
+    let sel_str = match selection {
+        Selection::FirstId => "1",
+        Selection::SecondId => "2",
+        Selection::All => "1:*",
+    };
 
-    let read = read_lines(imap, &mut buffer, Some(&b"40 OK FETCH"[..]))?;
-    let srv_msg = std::str::from_utf8(read)?;
+    let kind_str = match kind {
+        FetchKind::Rfc822 => "RFC822",
+        FetchKind::Rfc822Size => "RFC822.SIZE",
+    };
 
-    let ref_mail = match r#ref {
-        Email::Basic => EMAIL2,
-        Email::Multipart => EMAIL1,
+    let mod_str = match modifier {
+        FetchMod::None => "".into(),
+        FetchMod::ChangedSince(val) => format!(" (CHANGEDSINCE {})", val),
     };
-    let orig_email = std::str::from_utf8(ref_mail)?;
-    assert!(srv_msg.contains(orig_email));
 
-    Ok(())
+    imap.write(format!("40 fetch {} {}{}\r\n", sel_str, kind_str, mod_str).as_bytes())?;
+
+    let read = read_lines(imap, &mut buffer, Some(&b"40 OK FETCH"[..]))?;
+    let srv_msg = std::str::from_utf8(read)?;
+
+    Ok(srv_msg.to_string())
 }
 
 pub fn copy(imap: &mut TcpStream, selection: Selection, to: Mailbox) -> Result<()> {
@@ -281,29 +347,59 @@ pub fn append_email(imap: &mut TcpStream, content: Email) -> Result<()> {
     let read = read_lines(imap, &mut buffer, None)?;
     assert_eq!(&read[..5], &b"47 OK"[..]);
 
-    // we check that noop detects the change
-    noop_exists(imap)?;
-
     Ok(())
 }
 
-pub fn add_flags_email(imap: &mut TcpStream, selection: Selection, flag: Flag) -> Result<()> {
+pub fn search(imap: &mut TcpStream, sk: SearchKind) -> Result<String> {
+    let sk_str = match sk {
+        SearchKind::Text(x) => format!("TEXT \"{}\"", x),
+        SearchKind::ModSeq(x) => format!("MODSEQ {}", x),
+    };
+    imap.write(format!("55 SEARCH {}\r\n", sk_str).as_bytes())?;
     let mut buffer: [u8; 1500] = [0; 1500];
-    assert!(matches!(selection, Selection::FirstId));
-    assert!(matches!(flag, Flag::Deleted));
-    imap.write(&b"50 store 1 +FLAGS (\\Deleted)\r\n"[..])?;
-    let _read = read_lines(imap, &mut buffer, Some(&b"50 OK STORE"[..]))?;
-
-    Ok(())
+    let read = read_lines(imap, &mut buffer, Some(&b"55 OK"[..]))?;
+    let srv_msg = std::str::from_utf8(read)?;
+    Ok(srv_msg.to_string())
 }
 
-#[allow(dead_code)]
-/// Not yet implemented
-pub fn search(imap: &mut TcpStream) -> Result<()> {
-    imap.write(&b"55 search text \"OoOoO\"\r\n"[..])?;
-    let mut buffer: [u8; 1500] = [0; 1500];
-    let _read = read_lines(imap, &mut buffer, Some(&b"55 OK SEARCH"[..]))?;
-    Ok(())
+pub fn store(
+    imap: &mut TcpStream, 
+    sel: Selection, 
+    flag: Flag,
+    action: StoreAction,
+    modifier: StoreMod
+) -> Result<String> {
+    let mut buffer: [u8; 6000] = [0; 6000];
+
+    let seq = match sel {
+        Selection::FirstId => "1",
+        Selection::SecondId => "2",
+        Selection::All => "1:*",
+    };
+
+    let modif = match modifier {
+        StoreMod::None => "".into(),
+        StoreMod::UnchangedSince(val) => format!(" (UNCHANGEDSINCE {})", val),
+    };
+
+    let flags_str = match flag {
+        Flag::Deleted => "(\\Deleted)",
+        Flag::Important => "(\\Important)",
+    };
+
+    let action_str = match action {
+        StoreAction::AddFlags => "+FLAGS",
+        StoreAction::DelFlags => "-FLAGS",
+        StoreAction::SetFlags => "FLAGS",
+        StoreAction::AddFlagsSilent => "+FLAGS.SILENT",
+        StoreAction::DelFlagsSilent => "-FLAGS.SILENT",
+        StoreAction::SetFlagsSilent => "FLAGS.SILENT",
+    };
+
+    imap.write(format!("57 STORE {}{} {} {}\r\n", seq, modif, action_str, flags_str).as_bytes())?;
+    let read = read_lines(imap, &mut buffer, Some(&b"57 OK"[..]))?;
+    let srv_msg = std::str::from_utf8(read)?;
+    Ok(srv_msg.to_string())
 }
 
 pub fn expunge(imap: &mut TcpStream) -> Result<()> {
diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index 810fd79..cbe0271 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -88,3 +88,12 @@ pub fn read_lines<'a, F: Read>(
     println!("read: {}", std::str::from_utf8(&buffer[..nbytes])?);
     Ok(&buffer[..nbytes])
 }
+
+pub fn read_first_u32(inp: &str) -> Result<u32> {
+    Ok(inp
+        .chars()
+        .skip_while(|c| !c.is_digit(10))
+        .take_while(|c| c.is_digit(10))
+        .collect::<String>()
+        .parse::<u32>()?)
+}