What are pre-send mail tips in Outlook Assistant?

Pre-send mail tips validate recipients before sending an email. They check for common issues like out-of-office status, full mailboxes, and delivery restrictions — so you catch problems before hitting send, not after.

What are immutable IDs and why do they matter?

By default, Outlook message IDs change when emails are moved between folders. Immutable IDs stay the same regardless of folder moves, which means your AI agent can reliably track and reference specific emails over time.

How do batch operations work in Outlook Assistant v3.5.0?

Batch operations use the Microsoft Graph $batch endpoint to bundle up to 20 API requests into a single HTTP call. This significantly reduces latency when performing bulk operations like reading multiple emails or updating several calendar events.

Outlook Assistant v3.5.0 — Pre-send Mail Tips and Immutable IDs

Highlights

Pre-send mail tips

Validates recipients before sending — catches out-of-office, mailbox-full, and delivery restriction issues so you don't find out the hard way.

Immutable IDs

Messages keep the same ID even when moved between folders. No more broken references when organising your mailbox.

Batch operations

Bundle up to 20 Microsoft Graph API requests into a single call using the $batch endpoint. Faster bulk operations, fewer API round-trips.

What’s new in v3.5.0

I shipped three features that I’ve been wanting for a while — all focused on making the AI-to-Outlook connection more reliable and faster.

Pre-send mail tips

The new get_mail_tips tool checks recipients before your AI agent sends an email. It queries Microsoft Graph for delivery issues — out-of-office replies, full mailboxes, restricted recipients, external delivery warnings — and surfaces them before the email goes out.

This was something I kept running into personally: drafting an email through Claude, sending it, and then finding out the recipient’s mailbox was full or they’d left the company. Now the agent can check first.

Immutable IDs

This is a technical improvement that makes a big practical difference. Standard Outlook message IDs change when you move an email between folders — which meant if your AI agent saved a reference to a message and you later filed it, the reference broke.

Immutable IDs persist across folder moves. The agent can now reliably track emails over time without worrying about folder reorganisation breaking things.

Batch API support

For operations that touch multiple items — reading 10 emails, updating several calendar events — the agent can now bundle up to 20 Microsoft Graph requests into a single $batch call. Fewer round-trips, faster results, and kinder to API rate limits.

Tool count: 21

The tool count goes from 20 to 21 with the new get_mail_tips tool. The full set covers email, calendar, contacts, categories, folders, rules, settings, and shared mailboxes.