Try this to find the problem
% /usr/lib/sendmail -v
myname@mydomain.com < /etc/motd
You should be able to tell from the output where it is not working or where it is stopping.
Things it could be:
1. It may be a firewall issue - firewall not allowing the traffic.
2. Could be DNS is not set up correctly - you must have the PTR record or servers will refuse the mail
3. Your server isn't connected to the internet (obvious I know but...)
Check sendmail with this command
% /usr/lib/sendmail -d0.1 -bt < /dev/null
You should get something back like:
% /usr/lib/sendmail -d0.1 -bt < /dev/null
Version 8.9.3
Compiled with: MAP_REGEX LOG MATCHGECOS MIME7TO8 MIME8TO7 NAMED_BIND
NDBM NETINET NETUNIX NEWDB NIS NISPLUS QUEUE SCANF SMTP USERDB
XDEBUG
============ SYSTEM IDENTITY (after readcf) ============
(short domain name) $w = which1
(canonical domain name) $j = which1.mydomain.com
(subdomain name) $m = mydomain..com
(node name) $k = which1
========================================================
WARNING: Group writable directory /var
WARNING: Group writable directory /var/spool
ADDRESS TEST MODE (ruleset 3 NOT automatically invoked)
Enter <ruleset> <address>
>
Fix the warnings by changing the directory permissions. The most important thing is that the domain name system identity is correct - it should have the same type of entries for your server. If not, it may not work correctly.
Double check that the place you are sending to exist.
Post back.