diff --git a/.cursor/rules/notes.mdc b/.cursor/rules/notes.mdc
index 3ed52805ed..a15ec0f9c0 100644
--- a/.cursor/rules/notes.mdc
+++ b/.cursor/rules/notes.mdc
@@ -4,7 +4,7 @@ globs:
 alwaysApply: true
 ---
 - Do not try and run the project via `dev` or `build` command unless I explicitly ask you to.
-- Prefer self-documenting code over comments; use descriptive variable and function names instead of explaining intent with comments.
+- Prefer self-documenting code over comments; use descriptive variable and function names instead of explaining intent with comments. Never add comments that just describe what the code does - code should explain itself. Only add comments for "why" not "what".
 - Add helper functions to the bottom of files, not the top!
 - All imports go at the top of files, no mid-file dynamic imports.
 - Co-locate test files next to source files (e.g., `utils/example.test.ts`). Only E2E and AI tests go in `__tests__/`.
diff --git a/apps/web/CLAUDE.md b/apps/web/CLAUDE.md
index a0076ff2cd..ff36992fa3 100644
--- a/apps/web/CLAUDE.md
+++ b/apps/web/CLAUDE.md
@@ -20,7 +20,7 @@
 - Use proper error handling with try/catch blocks
 - Format code with Prettier
 - Consult .cursor/rules for environment variable management
-- Prefer self-documenting code over comments; use descriptive variable and function names instead of explaining intent with comments.
+- Prefer self-documenting code over comments; use descriptive variable and function names instead of explaining intent with comments. Never add comments that just describe what the code does - code should explain itself. Only add comments for "why" not "what".
 - Add helper functions to the bottom of files, not the top!
 - All imports go at the top of files, no mid-file dynamic imports.
 - Co-locate test files next to source files (e.g., `utils/example.test.ts`). Only E2E and AI tests go in `__tests__/`.
diff --git a/apps/web/utils/outlook/mail.ts b/apps/web/utils/outlook/mail.ts
index fbd1858143..5b7d8f2bfe 100644
--- a/apps/web/utils/outlook/mail.ts
+++ b/apps/web/utils/outlook/mail.ts
@@ -30,11 +30,13 @@ interface OutlookMessageRequest {
   isDraft?: boolean;
 }
 
+type SentEmailResult = Pick<Message, "id" | "conversationId">;
+
 export async function sendEmailWithHtml(
   client: OutlookClient,
   body: SendEmailBody,
   logger: Logger,
-) {
+): Promise<SentEmailResult> {
   ensureEmailSendingEnabled();
 
   const message: OutlookMessageRequest = {
@@ -59,11 +61,23 @@ export async function sendEmailWithHtml(
     message.conversationId = body.replyToEmail.threadId;
   }
 
-  const result: Message = await withOutlookRetry(
-    () => client.getClient().api("/me/messages").post(message),
+  await withOutlookRetry(
+    () =>
+      client.getClient().api("/me/sendMail").post({
+        message,
+        saveToSentItems: true,
+      }),
     logger,
   );
-  return result;
+
+  // /me/sendMail returns 202 with no body, so we can't get the sent message ID.
+  // Graph doesn't support filtering by internetMessageHeaders, so we can't query for it.
+  // conversationId (threadId) is preserved - that's what matters for reply tracking.
+  // Empty id means auto-expand won't work in EmailThread, but we don't show that for Outlook.
+  return {
+    id: "",
+    conversationId: message.conversationId,
+  };
 }
 
 export async function sendEmailWithPlainText(