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Mail offline because of too many connections?


Topic starter
Helping friend who recently migrated to an M1 MacBookAir. Her email had been setup as a mixed configuration of POP on her Mac and IMAP on her iPhone — not a good approach, so I preserved her POP emails, deleted the account, and set it up as IMAP. All is good except for one thing.
Every few days, the mail account on her Mac goes offline. Manually reconnecting occasionally works, but usually it needs several "take account online" selections. A couple times, it has taken 48 hours before it was willing to come back online — and when it stays off long term, she also sees the message “maximum number of connections from user IP exceeded, max number of connections=20” — which is weird because only her Mac and iPhone check this email account. But at least we have a clue -- the server "thinks" there are 20 connections coming at it.
When I research this error, it seems to be mostly a “POP-related issue”, but her account is most definitely setup as IMAP. Reading further, for some, the solution to this problem has been to increase the number of connections allowed by the server -- which implies having the admin rights to configure the server. Her mail host’s tech support is very hard to get ahold of, but we’re working on it.
Perhaps it’s time to switch mail hosts. But it sure seems that there’s a Big Sur element built into this problem.
Any ideas to prevent this situation, from the Mac side? She's running the latest Big Sur.
1 Answer

Quite a while since I’ve encountered this problem but it used to often be caused by Outlook holding too many IMAP connections open to Gmail. (I think it was a combination of fix to Outlook as well as limit increased by Google that resolved the issue.)

I don’t have the exact command to hand, but “netstat” from the terminal (or network utility) can help you confirm how many IMAP channels are being held open from the Mac.