I had the same problem. It start happened arround 3 months ago. It happened on all PC in my office.
When somebody in my office send an email, sometimes it bounced back.
The problem is, the bounced back email is listed as sent on Microsoft Outlook.
This is really become trouble for sales department where they send many email as to corresponded with customer. The email at least addressed to 3 recipients. And within 1 day, they usually send arround 100 - 200 emails. And when they accidentally close the email proxy error message box without reading the subject, they will need to call more than 1 person to check which email that being bounced back.
I already called Symantec. So far there is no better sollution than disabling the email auto-scanning.
Last month, one of our PC badly infected by viruses.
I don't know where the virus come from.
There is a possibility that the virus come from email since I disabled all the Symantec email scanning.
Then we got a new PC to replace the infected PC.
I install the newest Symantec 10.1.8 on the new PC.
But when the user use it to send email, the problem come back.
I didn't disable the email auto scanning this time because Symantec said that the new MR8 (10.1.8) won't have the Email proxy error. But infact, it still happening on the new PC.
I really need a sollution for this problem because if I disable the email scanning again, there is a possibility that another PC will be infected like the last one.
Every 2 weeks, I full scanned all the PC with SEP and never encountered any virus, except the 1 PC.
Now, the case that I open with Symantec is still pending for answer.
And every time I called Symantec, I need to wait for about 1 hour, listening to some music, to be able to connect to "assinged engineer" even thought the engineer changed each time I called.
I think I'll try the ComboFix.
Even thought It was a new PC, maybe the user install a software that having spyware.
I will really appreciated if there is another sollution for me to try it out.
Disabling the Email Scanning is not a sollution for me because the email scanning disabling might lead to another victim of virus in my office.