One user on the domain geetting hundreds of spam messages a day all of a sudden. The Exchange server is protected by Symantec Mail Security with Premium Anti-Spam (Cost me a fortune). I have gone over the PC with a fine tooth comb and found nothing suspicious going on in terms of viruses, spyware, etc. Not sure what to do next. Any ideas would be very welcome. Have included a sample.
From: System Administrator
Sent: 09 July 2009 02:01
Your message did not reach some or all of the intended recipients.
Sent: 09/07/2009 01:57
The following recipient(s) could not be reached:
firstname.lastname@example.org on 09/07/2009 02:01
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<SNT0-MC3-F4.Snt0.hotmail.com #5.5.0 smtp;550 Requested action not taken: mailbox unavailable (64168608:3309:-2147467259)>