Sync Errors reported Outlook for Max Version 16.108.1

@Ulli Lindquist said

Comcast recently switched from own email server to Yahoo. Since the switch I continue to experience this issue.

I have helped Classic Outlook for Windows and New Outlook for Windows users connect using OAuth to their Comcast accounts that have been migrated to Yahoo, by letting Outlook start the auto discovery process for comcast.com but then switching it to Yahoo as the provider.

Can you use a similar technique in Outlook for Mac?

It requires removing the old Comcast account first, so be sure you have a backup/export of anything in "This Computer Only" folders, or any other data for the Comcast account that is only stored on your Mac, before you start.

Classic Outlook - Adding a Comcast account that has been migrated to Yahoo
Answer by "Hornblower409 Apr 16, 2026" in
https://learn.microsoft.com/en-us/answers/questions/5663018/outlook-wont-let-me-sign-into-my-imap-server

New Outlook - Adding a Comcast account that has been migrated to Yahoo
Answer by "Hornblower409 Apr 23, 2026" in
https://learn.microsoft.com/en-us/answers/questions/5868248/email-sync-error-on-new-comcast-email-account

The behavior matches known IMAP sync issues where messages intermittently disappear and reappear after a provider-side change (in this case, Comcast moving mail to Yahoo).

For IMAP Yahoo-based accounts in Outlook for Mac, there is a documented issue where folder content re-syncs repeatedly and messages seem to pop in and out of view. The recommended workaround is to switch from Legacy (Classic) Outlook for Mac to the new Outlook for Mac interface, which uses a different sync engine and avoids these problems.

Action steps:

1. Open Outlook on the Mac.
2. Turn on the New Outlook switch (usually in the upper-right corner of the Outlook window).
3. Sign in to the Comcast/Yahoo account again if prompted and allow it to complete a full sync.
4. Monitor the Inbox and Trash/Bulk folders to confirm that messages no longer appear and disappear repeatedly.

If the issue persists even in the new Outlook, remove the IMAP account from Outlook, add it back in the new Outlook interface, and let it fully resync.

References:

• IMAP Yahoo and AOL accounts might experience issues with re-syncing folder content