VBSpam testing methodology - pre-DATA filtering
Because products in the VBSpam tests are tested in parallel, they will see all email arrive from the same fixed IP address and with the same EHLO domain. It is thus not possible (and certainly not advisable) to use these for filtering.
Because the MTA that relays all emails to all products adds a Received header, many products use the content of this header. It is also possible to have the original IP address added in an extra header (e.g. X-Original-IP).
A third option is for the MTA to send an extra SMTP command, right after identifying itself using EHLO. This command will contain the sender's IP address, the corresponding reverse DNS domain and the HELO/EHLO domain used. An example of such a command is XCLIENT, which is an extension for the Postfix MTA. While products won't gain any more information, they are encouraged to use XCLIENT (or something equivalent), to emulate a real situation, where most of the spam is blocked before the DATA command has been sent.
