New problem with firewall

[Marcio A. Regalado]

Hi guys, I'm again asking for your help...

I've a FC4 linux box running behind a firewall... the thing is that the 
FC4 box has an e-mail server and an apache server running on it and I 
need them to be accesible on-line I've a Dynamic IP so I get all the 
trafic redirected by no-ip, and the apache server runs fine, the web 
page is ok on-line but I can't receive e-mail from internet can you guys 
please help me with this issue

Theank you very much in advance.