I have Exchange 2007 which we migrated from 2003. We have several Global Security groups and several Distribution Groups. We have several users that are on another Exchange server (Front End) and when those users attempt to send email to our Global Security groups the email never gets delivered, nor does it bounce, it just disappears. Users that are on the our server (Back End) can send to those groups no problem. Is it true that Exchange 2007 only supports Universal groups? I read that pre-existing Domain Global groups are supported, but why are users having trouble sending email? Should I convert all Global Security groups to Universal?