I've installed the mailman contrib for sme 6 on sme 7 and it seems to work so far - I haven't really been able to complete test it since the server rejects emails to the address because there is no user to accept the emails to.
I remember on 6.0.1 we had to setup a mail rule to allow these in - is there a contrib for 7 that allows that or is there another way to do it in 7?