I seem to have run across an odd problem. We have several domains. All of these domains use one email server at, w'll say, mail.foo.com.
The problem I am encountering is that, while most email coming into the server is fine, there are a few emails from other persons and doamins where the 'From' header gets set to something like 'user@mail.foo.com' instead of their proper domain, even though the return path is something like 'user@theirdomain.com'.
I have read through the forums and seem to find issues where the sending people get their 'From' header changed. There is nothing currently in 'local-host-names' and resolv.conf only has our ISPs DNS servers and 'search foo.com'. I have, however, been unable to determine if masquerading is on in sendmail.cf (due to unfamiliarity with sendmail), so I am not too sure about that. I did do 'grep foo.com /etc/sendmail.cf' and all it does is returns a comment at the top of the file.
Any suggestions on what else I should do to correct the problem (if it is correctable)?
Thanks in advance.