You have set up an MX record? If you do not have this set up you would not be able to receive mail.-------------------If your ISP is blocking Port 25 you would not be able to send mail.Have you tried sending through your ISP's Mail server using this panel?http://wiki.contribs.org/SME_Server:Documentation:Administration_Manual:Chapter13#E-mail_Delivery
Not sure if i should start another thread or not but when i send mail it does not arrive at the recipient.