Ticket updates not emailing out to non-AD users

We have a large number of users who are not in our AD. I add them to BOSS manually in groups that are not AD related and this works so that when the person emails us, a ticket is created in BOSS. However, if I use the Comment box in the web interface to reply, no email is generated to the non-AD user like it is for the AtD users. Is this just the way it works for non-AD users? Or have I missed something in the configuration?

Thanks,
Margaret