You can also setup your HFBK mail with an external program. The server settings for your HFBK mail address are:
incoming server / receiving:
Type: IMAP
Server: imap.hfbk.net
Port: 993
Username: max.mustermann@hfbk-hamburg.de
Connection security: SSL/TLS
Authentication method: Password, normal
Outgoing mail server / sending:
Type: SMTP
Server: mx.hfbk-hamburg.de
Port: 465
Username: max.mustermann@hfbk-hamburg.de
Connection security: SSL/TLS
Authentication method: Password, normal
In the recommended mail program Thunderbird it looks like this: