If you delete them, you'll regret it. Exchange uses them for several things, perhaps most importantly to map a user account to the mailbox object in the mailstore. I think it would be true to say that Exchange no longer uses those addresses for message routing. _____ From: exchangelist-bounce@xxxxxxxxxxxxx [mailto:exchangelist-bounce@xxxxxxxxxxxxx] On Behalf Of Arnold, Jamie Sent: Wednesday, November 14, 2007 10:16 AM To: exchangelist@xxxxxxxxxxxxx Subject: [ExchangeList] Does 2003 require X400 addresses? I can't find anything that says this definitively, but it was my understanding that Exchange 2003 and higher no longer uses X400 addressing within the org and that SMTP addresses are all it requires to function. True? Thanks