sendmail not able to receive mails

Hello Everyone,

I have installed sendmail on my linux box. I am not able to receive mails from my domain itself. My linux box is behind a firewall. But when I send mails from another mail account in the same network I am not abel to receive mails. can any one of you please help me. I am able to tlenet to port 25. And when I type rcpt to: some user it says relaying done.