Microsoft has fixed synchronization problems between classic Outlook and Gmail or Yahoo accounts in its 365 service. The issue caused error codes 0x800CCC0F and 0x80070057 and prevented affected users from syncing their emails.
The fix is now live, but some users might still encounter temporary problems due to authentication tokens. Microsoft advises waiting for the OAuth token to expire or changing the password to restart syncing.
In the meantime, users can manually trigger a sign-in prompt by deleting registry entries related to the affected email account and restarting Outlook. This workaround is available on the company’s support pages.
Source: https://www.ghacks.net/2026/03/25/microsoft-resolves-outlook-gmail-and-yahoo-sync-errors-in-microsoft-365-service