Resolving Microsoft 365 / Outlook.com Sign-in Errors in Airmail (Account Invalid, Mail.outlook.com Cannot Be Loaded)

Some Airmail users on macOS report sign-in errors when adding a Microsoft 365 or Outlook.com account, such as "Account Invalid" or "Mail.outlook.com cannot be loaded", even after approving the request in the Microsoft Authenticator app. This article lists simple steps that resolve the issue in most cases.


When this happens


The error usually appears in one of the following situations:

  • Adding a personal Outlook.com or Hotmail account for the first time
  • - Re-adding an existing Microsoft 365 (work / school) account after a password change
  • - Returning to Airmail after an extended period without opening the app
  • - After Microsoft has rolled out OAuth or conditional-access policy changes

Quick checks before troubleshooting


  • Make sure macOS and Airmail are updated to the latest version available on the Mac App Store.
  • - Confirm the device has a stable internet connection and is not behind a VPN or proxy that blocks Microsoft endpoints (login.microsoftonline.com, outlook.office365.com).
  • - Verify that you can log in to https://outlook.live.com (personal) or https://outlook.office.com (work/school) using a web browser with the same credentials.

Step-by-step resolution


  1. Remove the account from Airmail
  2. - Open Airmail and go to Preferences (Cmd+,).
  3. - Select Accounts in the sidebar.
  4. - Click the failing Outlook / Microsoft 365 account, then click the "-" button to remove it.
  5. Quit Airmail completely
  6. - Press Cmd+Q to fully quit the app (closing the window is not enough).
  7. - Wait a few seconds, then re-open Airmail.
  8. Re-add the account using Microsoft 365 / Outlook.com
  9. - Click "+" in Accounts and choose "Microsoft 365 / Outlook.com".
  10. - When the Microsoft sign-in window opens inside Airmail, complete the entire web sign-in flow including any "Stay signed in" and consent screens.
  11. - Approve the request in the Microsoft Authenticator app when prompted, then return to the Airmail sign-in window and wait for it to close on its own.
  12. If OAuth keeps failing, add the account via IMAP
  13. - Click "+" in Accounts and choose "Other (IMAP)".
  14. - Use the following settings:
  15. - Incoming (IMAP): outlook.office365.com, port 993, SSL
  16. - Outgoing (SMTP): smtp.office365.com, port 587, STARTTLS
  17. - For accounts with 2-Step Verification, generate an App Password at https://account.microsoft.com/security and enter that as the password instead of your normal one.
  18. For work or school accounts
  19. - Some Microsoft 365 tenants enforce Conditional Access policies that block third-party email clients. If steps 1–4 do not resolve the issue, contact your IT administrator and ask them to allow Airmail (or any third-party IMAP / OAuth email client) for your account.

Still not working?


If the error continues after the steps above, contact Airmail support and include:

  • A screenshot of the exact error message shown by Airmail
  • - Your Airmail version (Airmail menu > About Airmail)
  • - Your macOS version
  • - Whether the account is a personal Outlook.com / Hotmail account or a Microsoft 365 work / school account

This information helps us identify whether the issue is related to your account configuration, your network, or a Microsoft-side policy.

Updated on: 05/15/2026

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