Not sure when this happened, but a plain "w" somehow got listed in the SURBL, at least in the text list version. I've perused the website and the list removal section, but haven't found a way of determining what the source of the "w" is, since the query tools do domain format checking and won't let me query on a plain "w".
The "w" shows up in this list: http://www.surbl.org/dns-queries.blocklist.counts.txt It's in the section preceeded by the number "2".
The effect of this is that domains that have a "w" in certain places generate false positives.
It might be a good idea to run new domains through a simple domain format parsing check to make sure that they're basically valid before adding them to the SURBL.
John DeMillion Director of Information Technology Chester County Intermediate Unit