Stupid, stupid me. I had to reset the factory settings on my router and didn't record the port forwarding rules before i dd the reset.
Could anyone tell me wich ports besides the following i need additionaly to be forwarded?
HTTP-Server TCP 80
FTP-Server TCP 21
SMTP TCP 25
Imap TCP 143
POP3 TCP 110
SSMTP TCP 465
IMAPS TCP 993
POP3S TCP 995
HTTPS-Server TCP 443
Thank you