Our email servers ban IPs that produce many failed login attempts for security reasons.
To double check this is the case, just try connecting via another network (e.g. Wifi / 4G). If it connects or says "wrong password" then it's surely a ban.
In the case of a ban visit whatismyip.com and attach a screenshot of the box with your IP address in your ticket. After clearing your ban we will also find the culprit with the wrong password, find the password or reset it as needed.
If that's not the case run the command tracert for Windows, or traceroute for Linux/Mac, followed by your email server address (e.g. mail.mydomain.com) and attach a screenshot of the results in your ticket; so that we can pinpint any network issues.
P.S. There is a really small chance our server is down, but we feed him with fiber daily to keep him happy. You can see the status of out servers at https://status.dws.gr/status/dws.