Probably the most useful information is how to cloak the url.
I understand url cloaking is done using frames (defining only one), but I can't help much with html. You could have a look here for some guidance there.
http://www.dslreports.com/forum/rema...monk~mode=flat
So you could configure a subdomain with a redirect inside a frame to your mail server, and all surfing within the mail server would be inside the frame which would have the address of the frame.
Other solutions all require a different port I think
Hope there's some help there