Zeitüberschreitung bei IMAP-Serververbindung, SMTP-Serververbindung funktioniert tadellos

Posting a screenshot of the server setting pane may help so volunteers here can see what your settings are. thank you

I've cut it into 2 sheets.

Your IMAP server settings are in the 'server settings' pane for the account. That is what we need for a volunteer here aware of your general account issues to respond. Also, you might also try this, on the assumption that the setting is correct:

1. click to settings>general
2. scroll to the bottom and, on the right, is 'config editor'. click that
3. enter this: mailnews.tcptimeout
4. I think you will see the default setting is 100. Change to 250 save and exit
5. restart thunderbird and see if that works. Also, recheck config editor to be sure your change took.

I changed the default setting to 300 and I rechecked it, but it won't work. The server imap.ionos.de shows several times, that it can't be reached. The ionos-server smtp.ionos.de is reached in a second. Only my ionos accounts have this problem. My Gmail-account runs very well.