Maybe the same guy, but Campbell Murray wrote:

https://github.com/rapid7/metasploit-framework/blob/master/modules/auxiliary/scanner/smtp/smtp_relay.rb

so I don't think so? Hard to tell, since I've never been able to find a twitter / github profile for @xistence with a government-issued-sounding name.

Assuming you're not actually Campbell, then author credits are additive.