Possibly interesting... but these are rules about outgoing SMTP servers (MSAs), yes? How much of a relation does the outgoing SMTP server for a domain have to the canonical set of receiving SMTP servers (MTAs) for the domain held in the domain's DNS MX record? These can certainly be one and the same server; but it's not a requirement. So how often are they in practice? Especially for people actively trying to evade these sorts of RBLs?