I have this problem that's been bothering me for a few weeks now. In my Apple Mail on MacBook Pro I have 4 Mailboxes. One of them is Gmail synced via IMAP.
When I open the app everything works fine for about an hour, then an exclamation point next to my Gmail inbox appears saying "Too many simultaneous connections". This is nonsense because this is the only app accessing the e-mail. I know its creating more connections in background but…
The problem is that after this hour elapses, the whole Mail app is kind of frozen. Sending e-mails stops at 80% and won't finish (even all other mailboxes) and the app doesn't synchronize all the mailboxes at all. From time to time the whole app crashes completely.
Any ideas what could be wrong and Where to look for more details about this? Anyone with similar problems? Thank you!
Best Answer
check this link - gmail changed their authentication method without notice, so you have to make this change. You will get a confirmation email from gmail that seems scary - but it isn't. You haven't just opened your email to the world as they try to scare you to believe. Unfortunately, as usual, they don't work in concert with major software developers and we are left to pick-up the pieces as best we can.
https://productforums.google.com/forum/#!topic/gmail/lCjm9oim5Vo