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Microsoft 365

Connect your Microsoft 365 mailbox so your AI can read your mail and prepare drafts, as you or as a Shared Mailbox. You review and send every email from Outlook.

Last verified: 2026-09-28

Microsoft 365 is a Personal Connection: each Member connects their own work account, and the credentials and mail stay with that Member. Once connected, your AI can read your mail and prepare email drafts. CompanyOS never sends email from Microsoft 365. Every email action creates a draft that you review and send from Outlook.

Not yet verified end to end. The CompanyOS side is built and tested. The Microsoft admin-consent and Exchange Shared Mailbox steps below have not yet been walked through against a live Microsoft 365 organization. Treat the Microsoft-side wording as a guide to what your admin must grant.

Connect your mailbox

  1. In CompanyOS, open Mailbox and start the Microsoft 365 connection.
  2. Sign in with your Microsoft 365 work account and accept the consent screen. CompanyOS asks for User.Read, Mail.ReadWrite, Mail.ReadWrite.Shared, and Calendars.ReadWrite.
  3. Check that Mailbox shows connected.

Personal Microsoft accounts (Outlook.com) are not supported. If sign-in stops with “admin approval required”, your organization limits user consent: send your admin the scope list above.

Draft as a Shared Mailbox (admin required)

Skip this if you only draft as yourself.

Mail.ReadWrite.Shared does not by itself give access to a Shared Mailbox. A Microsoft 365 admin must grant you Send As or Send on Behalf on each Shared Mailbox, in the Exchange admin center or with PowerShell. Without that grant the mailbox won’t appear as a sender, and CompanyOS won’t fall back to another identity.

What your AI can do

Your AI finds the Mailbox App with find_apps and calls its operations with call_app:

Operation What it does
microsoft-365/read_mail Reads mail in your connected mailbox
microsoft-365/list_senders Lists who you can draft as: yourself, plus any Shared Mailbox you have rights to
microsoft-365/create_draft Saves a draft in Outlook with exact recipients, subject, and body
microsoft-365/send_history Lists the drafts prepared through CompanyOS

A saved draft is reported as drafted, never sent. A known failure is failed. An unclear provider response is unknown, so the AI doesn’t retry and create a duplicate.

Never ask your AI to invent a From address. If a sender isn’t in list_senders, it isn’t available.

Drafts from Scheduled Procedures

When a Scheduled Procedure prepares an email, the draft is created in the mailbox of the Owner who made the schedule. CompanyOS never uses another person’s mailbox. If that mailbox is disconnected, the run fails and the Owner gets a notice.

Not available: HTML email, attachments, BCC, mailing lists, or bulk sends.

Reconnect

A token can’t gain new permissions by itself. If CompanyOS adds a scope, or your admin changes what is approved, disconnect and reconnect under Mailbox. Do the same when the connection shows Reconnect.

Troubleshooting

  • Connected, but no Microsoft 365 operations appear. Ask your AI to refresh its tools. If they’re still missing, reconnect.
  • A Shared Mailbox is missing from senders. The Exchange Send As or Send on Behalf grant is missing or was removed. Ask your admin.
  • A draft fails with a sender error. Follow the recovery step in the error. Don’t retry as a different identity.