If I get what you are trying to do, I think you can do this if you can setup another ironmail system (e.g. an Ironmail 7.0 VM).
1 - set up a content rule to match the static address part in the header and perform the reroute action. Route to a second ironmail system. Email not matching the entire static string would be passed into your mail system normally and unaffected.
2 - On the second ironmail system (which would only see email fully matching the static address *.email@example.com) masquarade 'domain.edu' to your google alias domain so it sends the mail out.