strobe-classb 1.7 – strobe-classb is a very small, fast scanner which operates over class B networks and a perl script which uses it to scan for open e-mail relays.
You can download it from the following link: https://packetstormsecurity.com/files/download/14265/strobe-classb-v1.7.tgz
Source: https://packetstormsecurity.com/files/14265/strobe-classb-v1.7.tgz.html