Unable to Login to Outlook - Able to Login to other Microsoft Apps (Teams, Excel, Word, OneNote)

Dear @Alan,

Good day, and I appreciate the clear explanation of your concern. As a forum moderator, I genuinely wish I could directly access your account or delve into the backend systems to diagnose and fix this for you. However, our role here is limited to providing general guidance and solutions that can be applied by users. 

From my research, this issue is typically related to the Outlook app’s stored authentication state, cached credentials, or its interaction with an MDM‑enrolled device, rather than your actual password or account itself. The quickest way to determine and resolve problems of this nature is often to contact your organization’s IT department.

In the meantime, please try the steps below to see if they help. Please note that some steps or menu paths may vary slightly depending on your iOS version.

1.Sign out of all Microsoft apps and sign back in

• In any working Microsoft app (e.g., Teams or Excel): Go to your profile icon > Sign out of the work account.
• Do this for Teams, Excel, Word, OneNote, etc.
• Then try signing into Outlook fresh.

2.Remove the work account from iOS Settings

• Go to Settings > General > VPN & Device Management (or Profiles & Device Management).
• Look for your company's MDM profile and any "Work" or "Microsoft" / Entra ID accounts.
• If you see the work account listed under Passwords & Accounts or Mail / Contacts / Calendars, remove it.
• Also check Settings > Mail > Accounts or Settings > Passwords for any saved Microsoft work entries and remove them.
• Restart the iPad, then reopen Outlook and add the account again.

3.Reset or reinstall the Outlook app

• Offload the app: Settings > General > iPad Storage > Outlook > Offload App (keeps data) or Delete App.
• Restart iPad.
• Reinstall Outlook from the App Store.
• When signing in, carefully enter your full work email and password. If prompted for MFA, complete it fully.

4.Check for pending MDM/Company Portal actions

• Open the Microsoft Intune Company Portal app (if installed) or check in Settings > General > VPN & Device Management.
• Ensure the device shows as Compliant.
• Look for any required updates, policy refreshes, or certificate issues, apply them if shown.
• In some cases, re‑enrolling the device (if permitted by your IT department) or syncing the management profile can resolve authentication issues between Outlook and your work account.

This issue is commonly reported with iOS/Android Outlook + work accounts and MDM, and the account removal + reinstall steps resolve it in most cases but if the issue persists, please contact your IT administrator and provide the exact error message, tag, and correlation ID.

They can check Entra ID sign-in logs for this correlation ID (it often reveals the exact rejection reason on the backend, such as a conditional access policy, certificate mismatch, or token issue specific to the Outlook client on iOS and resolve it for you. If you don't know who your IT administrator is, please refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support 

I hope this information is helpful. Please follow these steps and let me know if it works for you. If you have any questions or need further assistance, please feel free to share them in the comments so I can continue to support you. Thank you for your patience and understanding. I'm looking forward to your reply.

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Based on the error and the fact that sign-in works in OWA and on other devices, the issue is specific to Outlook on the iPad and/or the stored credentials on that device.

Try these steps in order:

1. Confirm account and password

• Use a browser on the iPad (e.g., Safari) and sign in to Outlook on the web with the same work account to confirm the credentials work on that device.

2. Reset Outlook mobile sign-in

• Make sure the Outlook app is updated to the latest version from the App Store.
• In Outlook for iOS, sign out of the work account if it appears partially added.
• Remove the work account profile from the iPad’s device management or mail profiles if it was added separately via iOS Mail.

3. Clear any cached sign-in and re-add the account

• Delete the Outlook app from the iPad.
• Restart the iPad.
• Reinstall Outlook from the App Store.
• Open Outlook and add only the work account again, following the modern authentication flow.

4. If using Apple Mail instead of Outlook

• If the work mailbox was also added in Apple Mail, remove it and re-add it as an Outlook.com/Exchange Online account so it uses OAuth instead of basic auth, as described under “If you use Apple Mail.”

5. If sign-in still fails only in Outlook mobile

• For a work or school account, use the self-service password reset link if enabled, or contact the organization’s IT admin to check for any conditional access, device compliance, or MDM policies that might be blocking Outlook mobile specifically. They may need to review sign-in logs and device registration status.

If none of the above resolves the issue, the admin should open a support case with Microsoft using the correlation ID and error details from the failing sign-in on the iPad.

References:

• Can't sign in to the Outlook mobile app
• Outlook and other apps are unable to connect to Outlook.com when using Basic authentication
• What you can do in the Microsoft 365 apps on mobile devices with a Microsoft 365 subscription