From 2c04d4473c6dd44c4a8afd5ae4a4fec37bedc33e Mon Sep 17 00:00:00 2001
From: Maurus Decimus <11444311+mdecimus@users.noreply.github.com>
Date: Sun, 19 Jul 2026 16:02:20 +0200
Subject: [PATCH] Fix IMAP: Pipelined `STORE` and `EXPUNGE` can execute out of
 order

---
 CHANGELOG.md                   |  4 +++-
 crates/imap/src/core/client.rs |  5 ++++-
 crates/imap/src/op/store.rs    | 13 +++++++++++--
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5b07c6f6..67954903 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,7 +11,9 @@ If you are upgrading from v0.16.x, replace the binary (or run `docker pull`). If
 ## Changed
 
 ## Fixed
-- IMAP: Mailbox object-quota only enforced in JMAP.
+- IMAP:
+  - Mailbox object-quota only enforced in JMAP.
+  - Pipelined `STORE` and `EXPUNGE` can execute out of order.
 - JMAP: 
   - Read-only sharee cannot set `isSubscribed` on a shared mailbox.
   - Web Push payloads with `Content-Encoding: aes128gcm` should not be base64-encoded but sent as raw bytes.
diff --git a/crates/imap/src/core/client.rs b/crates/imap/src/core/client.rs
index a3a703b9..bd3cb9f9 100644
--- a/crates/imap/src/core/client.rs
+++ b/crates/imap/src/core/client.rs
@@ -30,11 +30,14 @@ impl<T: SessionStream> Session<T> {
         let mut bytes = bytes.iter();
         let mut requests = Vec::with_capacity(2);
         let mut needs_literal = None;
+        let mut has_expunge = false;
 
         loop {
             match self.receiver.parse(&mut bytes) {
                 Ok(request) => match self.is_allowed(request).await {
                     Ok(request) => {
+                        has_expunge |=
+                            matches!(request.command, Command::Expunge(_) | Command::Close);
                         requests.push(request);
                     }
                     Err(err) => {
@@ -140,7 +143,7 @@ impl<T: SessionStream> Session<T> {
                     .await
                     .map(|_| SessionResult::Continue),
                 Command::Store(is_uid) => self
-                    .handle_store(request, is_uid)
+                    .handle_store(request, is_uid, !has_expunge)
                     .await
                     .map(|_| SessionResult::Continue),
                 Command::Copy(is_uid) => self
diff --git a/crates/imap/src/op/store.rs b/crates/imap/src/op/store.rs
index f1c9b096..40837cac 100644
--- a/crates/imap/src/op/store.rs
+++ b/crates/imap/src/op/store.rs
@@ -43,6 +43,7 @@ impl<T: SessionStream> Session<T> {
         &mut self,
         request: Request<Command>,
         is_uid: bool,
+        spawn: bool,
     ) -> trc::Result<()> {
         // Validate access
         self.assert_has_permission(Permission::ImapStore)?;
@@ -52,13 +53,21 @@ impl<T: SessionStream> Session<T> {
         let (data, mailbox) = self.state.select_data();
         let is_condstore = self.is_condstore || mailbox.is_condstore;
 
-        spawn_op!(data, {
+        if spawn {
+            spawn_op!(data, {
+                let response = data
+                    .store(arguments, mailbox, is_uid, is_condstore, op_start)
+                    .await?;
+
+                data.write_bytes(response).await
+            })
+        } else {
             let response = data
                 .store(arguments, mailbox, is_uid, is_condstore, op_start)
                 .await?;
 
             data.write_bytes(response).await
-        })
+        }
     }
 }