I have 3 mailboxes in IIS 6 on my server 2003 machine, and I'm having issues with 1 of the accounts. When I try to send an e-mail to this account i get an error message:
Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 Unknown user - DYN001 (state 14).
I have tried deleting the mailbox/user account on Server 2003 and recreating it, but I'm still getting this problem. The other two mailbox accounts work just fine, and I was using the same incoming/outgoing POP3 settings on all 3 accounts.