You can check this in address test mode, sendmail -bt, but you need to remember to check it for header sender, header recipient, envelope sender, and envelope recipient (which should never be masqueraded) So the following list of tests would do this:

      sendmail -bt
      > /tryflags hs                      (test the header sender)
      > /try esmtp user@host.your.dom
      > /tryflags hr                      (test the header recipient)
      > /try esmtp user@host.your.dom
      > /tryflags es                      (test the envelope sender)
      > /try esmtp user@host.your.dom
      > /tryflags hr                      (test the envelope recipient)
      > /try esmtp user@host.your.dom
      > ^D                                (exit with control D)

This is rather cumbersome so a different way to test it is with Rob Kolstad's checksendmail perl script. You can get it from my ftp site:

      ftp.harker.com:/pub/sendmail/checksendmail

You can use it in normal mode giving it a list of addresses check in an address.resolve file, or you can use it to test one address:

      checksendmail -T user@host.your.dom

Checksendmail shows how a message whould be delivered with the /parse test which returns a mailer, host, user triple. Then for each mailer discoverd in this first step, checksendmail shows how the mailer will rewrite the recipient and sender addresses with the /try test. It is quite a useful debugging tool for sendmail