I too am having an issue similar to the one posted on 7/13/06. Symantec warning: "Your email message was unable to be sent because your mail server rejected the message".
There are a series of boxes which appear - each with a different number of out-going emails. The other odd thing is that the internet is very active, and the network shows our computer is receiving information (we have no other updates or active downloads).
Some show 207, 1021, 68. The numbers appear random. These appear to beoutgoing emails to what seems random users are "trying to be sent out". Many have a yahoo address. Symantec appears to error-out with messages saying "Your email message was unable to be sent because your mail server rejected the message".
I am running Windows XP pro sp2 and my email client is MS Outlook Express. I'm using 2006 Norton SystemWorks 2006 . I am seeking a solution to find the cause of this bugger.
I've unstalled Norton System Works 2006 and reinstalled (thinking the NSW was compromised). This did not resolve the issue.
I've also loaded Microsoft's Defender (Beta 2) x86 and the Microsoft Windows Malicious Software Removal Tool (KB890830). Both reported no errors of problems with our system.