Every once in awhile one of my internal users will send an email to an external address. The sender ends up receiving this error message:Your message did not reach some or all of the intended recipients.Subject: email address...Sent: 3/5/2009 10:32 AM The following recipient(s) cannot be reached: user@externaldomain.org on 3/5/2009 10:33 AM You do not have permission to send to this recipient. For assistance, contact your system administrator. <exchange.internaldomain.local #5.7.1 smtp;550 5.7.1 Unable to relay for user@externaldomain.org>This does not happen all the time and usually it is only to one individual at different times. Any suggestions on where to begin?Windows XP Pro, Outlook 2007 connection to an Exchange 2003 server with SP2

Hi,This might give some hints:http://www.eggheadcafe.com/forumarchives/Exchangeconnectivity/Oct2005/post24122428.aspLeif

Hi Phill,1. Would you please let me know how the Outlook connects to Exchange Server? RPC or POP3/SMTP?2. Please check the message header of the NDR message to check which server generate the NDR message3. If your Exchange 2003 server generates the NDR message, please check the SMTP log of the Exchange Server to check which remote SMTP server the Exchange attempts to deliver the message.If the Exchange Server delivers the message to external domain SMTP server directly, please check whether the remote server is the correct server of the external domain according to the MX record. If the remote server is correct, I suggest you contact the remote server admins as their server reject the message due to Unable to relay.Mike