Microsoft 365 business mailboxes connect over OAuth in the same way as Google. Personal Outlook.com accounts are supported where Microsoft permits application sending for them.
Connecting
- Go to Mailboxes and choose Connect mailbox.
- Select Microsoft.
- Sign in with the account for the mailbox you want to send from.
- Review the permissions Microsoft shows and choose Accept.
- Send a test email and verify it arrived.
- Assign the mailbox to the markets it should send for.
If your tenant requires admin consent
Many Microsoft 365 tenants require an administrator to consent to third-party applications before users can authorise them. If you see "Need admin approval", ask your Microsoft 365 administrator to grant consent for Find New Customer. They can review the exact permissions being requested before approving.
Do not disable security policies
Sending limits
A Microsoft 365 mailbox on your own domain uses your plan’s full allocation: 250 a day per market on Starter, 500 on Growth, 1,000 on Professional. A personal Outlook.com, Hotmail or Live account is treated as a consumer account and limited to 250, 350 and 450 respectively.
Microsoft also enforces its own per-mailbox recipient and message rate limits, which vary by licence. Those sit above your plan allocation, and the platform respects them — it slows or stops rather than pushing through.
A named individual mailbox on your company domain is perfectly fine. It does not have to be sales@ or info@. What matters is that it is a real, separately-authenticated mailbox on a domain you control.