Can't get iNotes in-house after installing a firewall

We recently added a Linux-based firewall and can no longer access iNotes (Webmail) from in-house. I need to know which ports need to be open so I can change our setup.
iNotes runs on the standard Web port that you use for Domino. By default, it is port 80, but it can be any port you specify in the server document.

This was first published in October 2003