Linksys router and RH7.2

I have a linksys router configured to allow the following ports:

80 HTTP
53 DNS
25 smtp
110 pop

I have my webserver running ok - but my sendmail isn't. When connecting to
my mail remotely thru Squirrelmail i get an IMAP error. When i use a mail
client program i get the error 'can't connect to pop server'.

Like i said my webserver is working fine but mail server isn't. Any
suggestions or tips on how to use linksys with linux would be apreciated.

AFterDiGItaL
2003A.D.