Hello,
since about two or there weeks I have had a strange problem with sending mails through my GMX Germany account.
I have setup 2FA with GMX and created an app password for K9. This is the same for IMAP and SMTP. Immediately after entering the password, sending works - until the next day or so. Then it complains it cannot login to the SMTP server.
I check the password - looks good. I clear the password and enter it again, then sending works again, until the next day again…
What’s wrong here? Is this a problem with GMX or with K9? I am or better was using K9 latest beta from the PlayStore beta Program, then switched to Thunderbird beta yesterday, which has the same problem.