Looking at some logs, I noticed a bunch of entries for dns queries failing to things like: lame server resolving ‘14.182.8.69.ipwhois.rfc-ignorant.org. After some digging around on Google, I found a mailing list post from rfc-ignorant.org announcing the removal of the ipwhois.rfc-ignorant.org zone.

Looking at the SpamAssassin docs, this the right line to put in your local.cf to disable this particular test:
score RCVD_IN_RFCI 0

Yay, fewer log messages to look at every day.