Is this a new setup? You get this when you send to any address? Run Exchange Best Practice analyzer, possible there may be some misconfiguration within your SMTP VS. ________________________________ From: exchangelist-bounce@xxxxxxxxxxxxx [mailto:exchangelist-bounce@xxxxxxxxxxxxx] On Behalf Of Evan Mann Sent: Wednesday, August 09, 2006 3:02 PM To: exchangelist@xxxxxxxxxxxxx Subject: [ExchangeList] Problem with relaying for authenticated users Exchange 2003 SP2. Users get an error 550, recipient address rejected. no such user if they try to relay through the mail server. I'm doing tests using Outlook 2003 setup for IMAP. I enabled the advanced settings to require authentication on the outbound mail server., and the default relaying options are enabled which should allow this to work. I double-checked. I must be missing something obvious here?