Hello, so are you saying that you can't send emails outside of your local area network? <H4>Outgoing Mail
The process is different when sending mail via the mail server. PC and Linux workstation users configure their e-mail software to make the mail server their outbound SMTP mail server.
If the mail is destined for a local user in the mysite.com domain, then sendmail places the message in that person's mailbox so that they can retrieve it using one of the methods above.
If the mail is being sent to another domain, sendmail first uses DNS to get the MX record for the other domain. It then attempts to relay the mail to the appropriate destination mail server using the Simple Mail Transport Protocol (SMTP). One of the main advantages of mail relaying is that when a PC user A sends mail to user B on the Internet, the PC of user A can delegate the SMTP processing to the mail server. Note: If mail relaying is not configured properly, then your mail server could be commandeered to relay spam. Simple sendmail security will be covered later.
Try reading this page: Quick HOWTO : Ch21 : Configuring Linux Mail Servers - Linux Home Networking
If you think your problem is still with port forwarding then get back to me and I'll see what I can do.