IP masquerading not working for sendmail

[Kapil Khanna <boomkap usa net>]

I am running RHAT 7.2. I want to masquerade email being sent from this machine
as mydomain.com
According to the docs i set the DN entry to be DNmydomain.com in the
/etc/sendmail.cf file. I restarted sendmail (/etc/rc.d/init.d/sendmail
restart).
I tried sending an email from this box. However masquerading is not working :(
Thus all emails from my machine end up as junk mail on most public domains
like hotmail etc...