sendmail - changing root in the from address

Trying to change the from address from root@localhost.localdomain to user@mydomain.com
Using MASQUERADE options in sendmail.mc I was able to change the domain so now my emails are coming from root@mydomain.com
I am not able to find out how to change the to

I did some searches here and on the net but couldn't find a solution for RHEL

Any help/suggestion greatly appreciated

Thanks,