Apple Mail won't connect to GMX.com

[HandyMac]

I have several email accounts at gmx.com, which I access through IMAP via Apple Mail (macOS 10.12 Sierra, 15" 2014 MacBook Pro). Every now and then Mail says it can't access one or another of the accounts, tells me to enter my password in Internet Accounts Preference Pane. Sometimes it does work when I do this – though the password is the same as before. Sometimes I've found that if I quit Mail, then open it again, now it connects okay. Then sometime later (days, weeks, months) it stops working again.

Yesterday it did this again. I entered the password, it didn't work, I went to the gmx.com website and checked the password, it worked fine. So it's not the password. I quit Mail and restarted it, now it worked. Only ten minutes later, again it couldn't connect. Shortly it was unable to connect with any of the gmx.com accounts. And so it has been for several hours now, though I've quit and restarted Mail several times.

So I tried on my second, backup Mac, a 13" 2014 MacBook Pro, also with macOS 10.12 Sierra. Opened Mail, which had not been used at all, set up two of the gmx.com accounts; both work fine. So the problem is not the password(s), nor gmx.com, nor anything in my Internet connection, but something in the Apple Mail on my primary MBPro.

I know Mail has support files here and there in ~/Library/, but from previous experimentation I don't think any of them are concerned with accounts and passwords. These data seem to be hidden somewhere else, presumably for security reasons. I don't want to delete Mail and reinstall it, and have to go through all the hassle of importing all my old mail again. Is there some support file for Mail that may be corrupted, that can be deleted to get it to start fresh?

 

[w33tab1x]

Hi!
unfortunately, I've been having the same problem for several months now: A gmail email account which used to work properly in my Apple Mail app is not able to connect anymore. This is very annoying since I have to go to Gmail in my browser to check my emails, instead of having everything in the Apple Mail app.
It seems nothing works!
I've tried "Mail>Add Account" and also going to "System Preferences>Internet Accounts".
I always add my account, put in my gmail password, but NOTHING happens. The Gmail account still ist not working or even showing in the Apple Mail app.
Is there perhaps a limit, that only 2 email accounts can be used in the Mail App? Because I already have two other email accounts in my Mail App...
Thanks!

 

[HandyMac]

I see you've responded to an old post of mine. I eventually solved the problem, don't remember exactly how, so I can't offer any advice. Apple Mail is buggy, sometimes does weird things. You might try contacting Apple; I don't know which macOS version you're using, but they will answer questions about older ones – though sometimes the recently trained "advisers" don't know much about the older versions. Try: Get Support.