Translation - When setting up my existing email address "dem.ing@web.de" on this computer, I always get the message "Settings were found in the ISP database" after filling in the form. After clicking Done, I get the message "Login to the server failed; configuration, user name ... may be incorrect" after every attempt, even though everything is correct.

As I understand the TB functions, the first statement (Settings were found...) relates to setting up of the server names, ports and so on. the second statement (Login to the server...) relates more to the password, email address and so on.

Have you accessed your email provider's settings and entered/checked them manually? They're here, I think - https://hilfe.web.de/pop-imap/pop3/index.html

As I understand the TB functions, the first statement (Settings were found...) relates to setting up of the server names, ports and so on. the second statement (Login to the server...) relates more to the password, email address and so on.

Have you accessed your email provider's settings and entered/checked them manually? They're here, I think - https://hilfe.web.de/pop-imap/pop3/index.html

Your email provider has a web page dealing with what settings to change on their account before connecting to TB. I trust that you have followed their instructions? https://hilfe.web.de/pop-imap/pop3/index.html

Have you enabled POP or IMAP in web.de settings?

"Der Abruf von E-Mails über POP3 bzw. IMAP ist standardmäßig ausgeschaltet. Wenn Sie Ihre E-Mails mit einem E-Mail-Programm oder mit einer Mail App eines anderen Anbieters empfangen oder versenden möchten, müssen Sie POP3 bzw. IMAP einschalten. Loggen Sie sich dafür zunächst über www.web.de in Ihr Postfach ein."

https://hilfe.web.de/pop-imap/einschalten.html