I have two users who have been recieving messages like these for the last couple of days. I don't think that they are coming from my server. How do I determine where they are originating from?
Your message did not reach some or all of the intended recipients.
Subject: smiling to you, dear
Sent: 9/10/2010 7:33 AM
The following recipient(s) could not be reached:
firstname.lastname@example.org on 9/10/2010 7:33 AM
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<SNT0-MC3-F30.Snt0.hotmail.com #5.5.0 smtp;550 Requested action not taken: mailbox unavailable (1044235902:3448:-2147467259)>