[Sunhelp] a different sendmail problem

[sr]

I have something wrong in my sendmail configs that causes this problem:
If someone sends mail to me at sr at mydomain.com, I receive it addressed to
sr at www.mydomain.com.  Also, the e-mail I send is received from
sr at www.mydomain.com, even though my e-mail client configs say
sr at mydomain.com.  This happens with the e-mail accounts in the virtual
domains I host, as well.  Ideas?