Hey guys,
I am having troubles with emClient. Everytime I start it, it ask for my Password and says “unauthorized”. If I put in the password the same windows appears again. If i click cancel the window disappears for a few minutes. My E-Mails are downloaded anyways. Strange, isn’t it?
Can someone help me with this issue? It is really annoying to cancel the window every few minutes.. 
This means your email works fine, but the window keeps popping out for different service - synchronized calendar, contacts, etc.
You can try going to Menu > Accounts and select your account. Uncheck one service at a time to find out which one is causing the issue. If you are using Gmail or Outlook, you can try reauthenticating it by removing your account and adding it back.
If you are using a GMX address with 2FA enabled, GMX requires a separate app password for each service: IMAP (mail in), SMTP (mail out), and CalDAV/CardDAV (calendar/contacts). Using the same password across the whole account causes login failures for those other services. That might be what causes it.
For more information, please see this link:
GMX 2FA login problem with app passwords