So in setting up the site for a client I realized that the return-path is not being setup correctly. In our case the name of the site is "Media@McGill" and this is the name (attached to the smpt server's name) that is being sent. If I turn off MimeMail and use the DefaultMail system then it uses the proper email address configuration.
Any ideas? I even tried to change the "Sender name" to match the email address but that didn't seem to even be used?