feat: reply to the Reply-To address when the sender set one

crates/core/src/types.rs

@@ -916,6 +916,11 @@ pub struct MessageMetadata {
     pub text_html_source: Option<BodyPartSource>,
     pub calendar: Option<CalendarMetadata>,
     pub raw_headers: Option<String>,
+    /// Addresses from the `Reply-To:` header, if the sender set one.
+    /// Replies target these instead of `From:` (mailing lists and
+    /// no-reply senders rely on it). Empty when absent.
+    #[serde(default)]
+    pub reply_to: Vec<Address>,
 }
 
 #[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq)]

crates/daemon/src/handler/mutations.rs

@@ -1789,15 +1789,23 @@ pub(super) async fn prepare_reply(
         .map(|account| account.email)
         .unwrap_or_default();
 
-    let thread_context = match state.sync_engine.get_body(message_id).await {
-        Ok(body) => (*get_or_render_reply_context(state, message_id, &body)).clone(),
-        Err(_) => String::new(),
+    let body = state.sync_engine.get_body(message_id).await.ok();
+    let thread_context = match body.as_ref() {
+        Some(body) => (*get_or_render_reply_context(state, message_id, body)).clone(),
+        None => String::new(),
     };
 
     let self_address = from.to_ascii_lowercase();
-    // Envelope does not yet capture the Reply-To: header — using From: as the reply target
-    // covers the common case. Capturing Reply-To: properly is a post-v1 envelope schema change.
-    let reply_to = envelope.from.email.clone();
+    // Prefer the Reply-To: header when the sender set one — mailing lists
+    // and no-reply senders depend on it — falling back to From: otherwise.
+    // Reply-To is captured into the body metadata at parse time.
+    let reply_to = body
+        .as_ref()
+        .and_then(|body| body.metadata.reply_to.first())
+        .map_or_else(
+            || envelope.from.email.clone(),
+            |address| address.email.clone(),
+        );
 
     let cc = if reply_all {
         let mut seen: std::collections::HashSet<String> = std::collections::HashSet::new();

crates/daemon/src/handler/tests/mutations_and_delivery.rs

@@ -836,6 +836,53 @@ async fn dispatch_prepare_reply_renders_html_context() {
     }
 }
 
+#[tokio::test]
+async fn dispatch_prepare_reply_prefers_reply_to_header() {
+    let state = Arc::new(AppState::in_memory().await.unwrap());
+    let id = sync_and_get_first_id(&state).await;
+
+    // The original message carries a Reply-To distinct from its From
+    // (the mailing-list / no-reply case).
+    state
+        .store
+        .insert_body(&mxr_core::types::MessageBody {
+            message_id: id.clone(),
+            text_plain: Some("digest".into()),
+            text_html: None,
+            attachments: vec![],
+            fetched_at: chrono::Utc::now(),
+            metadata: mxr_core::types::MessageMetadata {
+                reply_to: vec![mxr_core::types::Address {
+                    name: Some("List Discussion".into()),
+                    email: "discuss@list.example.com".into(),
+                }],
+                ..Default::default()
+            },
+        })
+        .await
+        .unwrap();
+
+    let msg = IpcMessage {
+        id: 2,
+        source: ::mxr_protocol::ClientKind::default(),
+        payload: IpcPayload::Request(Request::PrepareReply {
+            message_id: id,
+            reply_all: false,
+        }),
+    };
+    match handle_request(&state, &msg).await.payload {
+        IpcPayload::Response(Response::Ok {
+            data: ResponseData::ReplyContext { context },
+        }) => {
+            assert_eq!(
+                context.reply_to, "discuss@list.example.com",
+                "reply must target the Reply-To header, not From"
+            );
+        }
+        other => panic!("Expected ReplyContext, got {other:?}"),
+    }
+}
+
 #[tokio::test]
 async fn dispatch_prepare_forward() {
     let state = Arc::new(AppState::in_memory().await.unwrap());

crates/mail-parse/src/lib.rs

@@ -446,6 +446,8 @@ fn extract_metadata(message: &Message<'_>, raw_headers: Option<String>) -> Messa
         .map(std::string::ToString::to_string);
     let text_plain_format = message.content_type().and_then(parse_text_plain_format);
 
+    let reply_to = message.reply_to().map(extract_addrs).unwrap_or_default();
+
     MessageMetadata {
         list_id,
         auth_results,
@@ -455,6 +457,7 @@ fn extract_metadata(message: &Message<'_>, raw_headers: Option<String>) -> Messa
         text_html_source: None,
         calendar: None,
         raw_headers,
+        reply_to,
     }
 }
 
@@ -777,6 +780,39 @@ mod tests {
         );
     }
 
+    #[test]
+    fn reply_to_header_is_captured_into_metadata() {
+        let raw = concat!(
+            "From: No Reply <no-reply@list.example.com>\r\n",
+            "Reply-To: List Discussion <discuss@list.example.com>\r\n",
+            "To: me@example.com\r\n",
+            "Subject: Weekly digest\r\n",
+            "Message-ID: <digest-1@list.example.com>\r\n",
+            "\r\n",
+            "Body.\r\n",
+        );
+        let metadata = parse_message_metadata_from_raw(raw.as_bytes()).unwrap();
+        assert_eq!(metadata.reply_to.len(), 1);
+        assert_eq!(metadata.reply_to[0].email, "discuss@list.example.com");
+        assert_eq!(
+            metadata.reply_to[0].name.as_deref(),
+            Some("List Discussion")
+        );
+    }
+
+    #[test]
+    fn absent_reply_to_leaves_metadata_empty() {
+        let raw = concat!(
+            "From: Alice <alice@example.com>\r\n",
+            "To: me@example.com\r\n",
+            "Subject: Hi\r\n",
+            "\r\n",
+            "Body.\r\n",
+        );
+        let metadata = parse_message_metadata_from_raw(raw.as_bytes()).unwrap();
+        assert!(metadata.reply_to.is_empty());
+    }
+
     #[test]
     fn calendar_metadata_backwards_compat_without_viewer_fields() {
         // Old JSON (no viewer_partstat, viewer_attendee_email, is_update)

site/src/content/docs/guides/compose.md

@@ -56,6 +56,10 @@ Hello from mxr.
 
 Reply and forward drafts include message context. If the original message only had HTML, mxr uses the rendered reader output, not raw HTML tags.
 
+## Reply recipient
+
+A reply targets the original message's `Reply-To:` header when the sender set one, falling back to `From:` otherwise. This is what mailing lists and `no-reply@` senders rely on — a reply to a list digest goes to the list, not the unmonitored sender address. `reply-all` adds the other original recipients as Cc on top of that target.
+
 ## Send confirmation
 
 After the editor closes, mxr shows a confirmation modal: