Perhaps, but...

Blacklists need to be targeted for contributing to the unreliability of email. The latest thing now is "greylisting" which is a similarly broken solution to SPAM. SPAM sucks, yes, but blocking systems that misrecognize even ONE legit email as spam should not be tolerated, unless it's one that you yourself installed on your own email accounts. The big problem with these blacklist systems, is lazy ISPs think they can make their life easier by imposing these braindead spam filters on their mail users, and in fact they DO make their life easier by reducing the overall amount of email traffic. But what that does to the reliability of legitimate email is criminal, or should be.

Another approach that e360 Insight could use is to sue their ISP for utilizing Spamhaus on their email accounts-- a far more effective tactic IMHO-- go after the Spamhaus customer base and hit them where it actually hurts. It might teach a few of those lazy ISPs to think twice before turning on filters that their customers can't choose to disable.