Mail stops checking for new mail until closed and re-opened
This problem began a month or so ago and is only getting worse by the day. I have my Mail app set to check for new mail every minute, but recently it randomly stops checking at all and displays the triangle icon next to each Inbox. I have 10 different email accounts that I use Mail to check and they are a variety of different types from Exchange servers, to IMAP accounts, to POP accounts, iCloud, Outlook.com, Gmail, etc. Part of the time only 2 or 3 inboxes are affected, while other times (more recently) it’s ALL accounts. Clicking on Get Mail doesn’t help; no new mail is downloaded. The only way to get Mail to “wake up” is to close the app and then re-open it. When I do that, there is a flood of new mail that pours in to each account that had been offline. There are never any error messages telling me that anything has happened. I just know that Mail is stuck because of the triangle icon.
Also, there are times when my busiest account mysteriously has no new messages over a few hours, which is very unusual. Closing and re-opening mail will resume downloading mail again to that account. At least for awhile...
I thought I’d solved the problem by thinking that my router was only working intermittently, so I replaced it with a new Time Capsule. The problem did not go away.
I’ve talked to Apple Support and they’ve not been any help. I’d welcome any suggestions.
iMac, OS X Mavericks (10.9.5), 3.4GHz Core i7 27 in. (mid 2011)