In case your operating system or e-mail program is not listed, here are some generally useful information.
Incoming mail server: mail.uni-kl.de
Outgoing mail server: smtp.uni-kl.de
Basically POP3S (Port 995) or IMAP (Port 993) are to be used. TLS is not allowed. Please note that secure authentication is enabled for sending e-mail. E-mail retrieval and sending works even without a VPN connection from outside the network of the TU Kaiserslautern.