If you receive an email claiming to be from an @vbulletin.com email address with text such as this:

Hello user of Vbulletin.com e-mail server,

Our antivirus software has detected a large ammount of viruses outgoing
from your email account, you may use our free anti-virus tool to clean up
your computer software.

For further details see the attach.

Sincerely,
The Vbulletin.com team http://www.vbulletin.com
It is not from the vBulletin team, and most likely contains a virus.