AFAIK, there is no outbound content filtering, although ST says they are thinking about adding it to SM. However, you can try Ultimate Spool Manager from mightyblue.com. It just might do the job for you. I'm using it for a similar purpose, for only one user, and it works fine for me. BTW SM Enterprise can be set to archive all emails, coming and going - not sure if that would be helpful for you in this regard.