Adding a Microsoft 365 account to Outlook for Mac

Connecting Outlook for Mac to a Microsoft 365 (Exchange Online) mailbox is usually straightforward, but there are a few quirks worth knowing about — especially in environments with Conditional Access or MFA policies.

Prerequisites

• Outlook for Mac installed (from the Mac App Store or your Microsoft 365 subscription)
• A valid Microsoft 365 mailbox
• Your UPN (User Principal Name) — usually your work email address

Steps

1. Open Outlook for Mac.
2. If this is a fresh install, the setup wizard launches automatically. If not, go to Settings → Accounts.
3. Click the + button and choose New Account.
4. Enter your email address and click Continue.
5. Outlook will detect that this is an Exchange Online account and redirect you to the Microsoft sign-in page.
6. Sign in with your credentials. If MFA is enabled, complete the verification.
7. If prompted, click Allow to grant Outlook access to your account.
8. Outlook will begin syncing your mailbox. Large mailboxes can take several minutes.

Common issues

Sign-in loop — If Outlook keeps asking for your password, the issue is usually a stale token. Go to Keychain Access, search for MicrosoftOffice, and delete the entries. Then try signing in again.

Conditional Access blocking — If your organisation has Conditional Access policies requiring a compliant device, your Mac may need to be enrolled in Intune (Microsoft Endpoint Manager) before the account will connect.

Modern Authentication disabled — Some older tenants have Modern Authentication disabled. You can check with your admin, or try toggling it in the Microsoft 365 admin centre under Settings → Org Settings → Modern Authentication.

Verifying the connection

Once sync completes, send a test email to yourself. If it appears in both the Sent folder and your Inbox (received from yourself), the connection is working correctly.