Hi all. A friend of mine recently had a problem with sending mail. users could send to root and that's all. no user to user or user to root or even root to user mail. he got user unknwon errors.it turned out that the problem was with upper cased user names. that is the first letter of every user name was in upper case. why is that a problem? or is it something well known that i simply missed? THX, Eran.