I recently moved a domain from an independent provider using IMAP/SMTP to a business Microsoft 365 tenant. The mail migration completed successfully, classic Outlook on Windows works, and MFA is configured.
The problem is Outlook Mobile on Android. I removed the old account, cleared Outlook's cache and data, uninstalled and reinstalled the app, and tried removing the old authentication entry. When I add [email protected], Microsoft detects both a personal and a work or school account. Choosing Work or School then produces this error:
"We're unable to complete your request — unauthorized_client: The client does not exist or is not enabled for consumers."
It seems Outlook Mobile may still have cached tokens or autodiscover information from the former IMAP setup and is sending authentication to the consumer endpoint. Authenticator still shows the account as a connected account used by other apps, so it cannot be removed normally. I would prefer not to remove Authenticator because many other accounts would need to be registered again. What should I try next, and could stale autodiscover or DNS information be responsible?
4 Answers
Also check whether the Android devices are enrolled in mobile-device management. An MDM policy or app configuration profile could be reinstalling an old Outlook account or forcing an outdated setup, even after clearing the app. If the devices are managed, review the Outlook configuration assigned to them.
Outlook Mobile can use different autodiscover behavior from desktop Outlook. After an IMAP-to-Microsoft 365 migration, stale autodiscover data may continue directing mobile clients to the old service or the wrong sign-in endpoint. If the Microsoft 365 DNS records are correct, the practical fix may be to wait for the cached data to expire. Microsoft support has reportedly resolved similar cases this way, although the delay can vary.
Try entering the tenant’s initial onmicrosoft.com address instead of the custom domain when adding the account. That can bypass a confused consumer-versus-work account lookup and send Outlook Mobile directly to the Microsoft 365 tenant. If that succeeds, the custom-domain autodiscover configuration is the likely issue.
Verify the domain’s Microsoft 365 DNS records, especially the autodiscover record and the mail-related records recommended in the admin center. A DNS propagation or stale-record problem can affect mobile setup even while desktop Outlook continues working. Microsoft’s Exchange connectivity testing tool can also check whether autodiscover is returning the expected result.
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