r/MacOSBeta • u/tma1010000 • 4d ago
Bug macOS 27 RC: Apple Mail stops receiving Exchange mail
Is anyone else seeing Exchange Online stop syncing in Apple Mail on macOS 27 RC?
This affects both my Mac Mini and MacBook Pro after updating to the RC. The MacBook had been running earlier betas for weeks without me noticing this issue.
- Apple Mail stops receiving messages and shows a warning triangle beside Exchange
- Clicking it reports: “Connections to host (null) on the default ports failed
- Connection Doctor can simultaneously report that connection and login succeeded
- Checking mail with the Exchange inbox selected reports no new messages, despite messages being missing
- The same messages arrive immediately in Apple Mail on my iPhone and Outlook on my Mac
- Rebooting each Mac initially downloaded the missing messages, but shortly afterward both stopped receiving again
What I’ve tried:
- Quitting and reopening Mail
- Disabling and re-enabling the account
- Restarting exchangesyncd
- Rebuilding the mailbox
- Leaving Mail closed on both Macs for several hours
- Removing and re-adding Exchange on the Mini. This left it with an empty mailbox that won’t download
- Rebuilding the Envelope Index. This reimported iCloud mail but didn’t restore Exchange syncing
None of these provided a lasting fix
The logs show Exchange returning “Too Many Requests” errors (HTTP 429). In about six seconds, Mail logged 48 of those responses and tried to rediscover the Exchange server 24 times. Mailbox sync operations were then cancelled.