Support, I recently setup a new domain on Exchange 2003 running on SBS 2003. I have added the new domain to the recipients policy and had it propogate to all users on the system. For Example ( Primary smtp : user@domain1 and the new domain is user@domain2). I have verified that the change has taken effect. My problem is when I try to send an email from outside to the address ( user@domain2) it returns immediately and give me this particular error. I can send an emailfrom internally and it will receive. User@domain2 on 9/11/2007 3:44 PM There was a SMTP communication problem with the recipient's email server. Please contact your system administrator. <farsightcomputer.com #5.5.0 smtp;550 HYPERLINK "mailto:User@domain2" User@domain2 unknown user account> I have read through several KB articles and have visited several forums looking for an answer. Everything I find tells me to make the change in the recipients policy and everything should work fine.

This is correct, create a new recipient policy or modify an existing one. the only thing that I can think is that there is another software installed on your Exchange server such as AntiSpam or AV.