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Bypass blockage of port 25

E-Mails are sent over the standard port 25. Also maleware use this port to send spam, therefore the external connection to mailservern from the network of the University of Cologne over port 25 (SMTP) is blocked. This may cause error messages when attempting to send emails.

Those affected are those who either:

  • are connected with the VPN over the Full-Tunnel mode or have a connection over WLAN with the UKLAN
  • or be in one of the subnetworks of the institutes

and simultaneously using a mail client (like Outlook, Thunderbird, Apple Mail) and want to sent e-mails over an external mail server (like GoogleMail, or

To bypass this blockage, configurate your mailclient to an alternative port. To sent e-mails use port 587.

If you have any questions or problems, please contact the RRZK-Helpdesk