I want to send a message from K-9 Mail to GMX server. GMX responds with “Failed to verify outgoing mail server settings. Authentication error. Invalid authentication credentials.” But all settings in k-9 mail for mail output server are correct. I don’t understand what happens. By the way, importing emails from GMX to K-9 Mail works perfectly.
Have you tried each pair of encryption and port numbers stated on the GMX support page here.
- Security: SSL/TLS, Port: 465
- Security: StartTLS, Port: 587
Are you using an App Password rather than your account password. If so, have you applied this on the outgoing server page.
Have you checked for typing errors when entering the password?
Are you using any Security, Antivirus or VPN application on your phone? If so, test with the software disabled.
Do you have any firewall enabled that could be blocking the SMTP port?
Zeroid, thank you very much; it was obviously a simple problem by a mistake in my very long password (upper-case instead of lower-case character). Nevertheless a good thing to join this forum. Best regards UFe