if you get ( doing a netstat -an more )

tcp 0 0 127.0.0.1:25 0.0.0.0:\* LISTEN

Then your sendmail server is configured to accept connections from localhost only.

To change this behavior, you need to edit /etc/mail/sendmail.mc. Find the line that starts with DAEMON_OPTIONS ( suggest vi +/DAEMON_OPTIONS sendmail.mc ) and edit the field Addr= to change it to your IP Address.

Then go down approx. 7 lines and comment out the line that reads:

FEATURE(\`accept\_unresolveable\_domains')dnl

Next, exit vi (or whatever editor you use) and do…

m4 /etc/mail/sendmail.mc \> /etc/sendmail.cf

Restart sendmail, and you should be able to receive mail from other mhosts