Ask Al: Checking email addresses against URIBLs?

Scott writes, "I use URIBL lists in SpamAssassin, and these are configured according to their documented purpose (URI checks). I am getting a lot of spam now which spamvertise email addresses, rather than a URI. The bad domain might be in the From: field, or it might be in the message body. Example: 'Contact me at this address'. These domains are already on RBLs such as URIBL_BLACK. The first question is, do you think this is a valid strategy, and how 'safe'? I can not see any negatives with the spam examples I have received. Second question is, how does one take advantage or URIBL etc to validate email address strings? Google for "spamassassin rhsbl" and you get no useful information."