I am getting this error when sending to a specific email address . I use Exchange 2003.I only have this problem with this address and have tried sending it from a hotmail account which works fine. Any ideas ?
Your message did not reach some or all of the intended recipients.
Sent: 16/04/2009 14:22
The following recipient(s) cannot be reached:
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<"mydomain.co.uk" #5.5.0 smtp;550 Submission from dynamic "my IP Address "requires authentication>