Resurrecting this post as well as the os_blacklistemail module. I'm replying to the post in case someone comes across it in a search.
I originally wrote the module in 2005, stopped using it in 2008, and then never bothered to so much as look at it again until a few days ago when someone was behaving in a manner on my network that would have made it useful to have.
I've "released" an untested, interim version (1.0.6) that's exactly the same as it was in the past except that it compiles against Anope 1.8.x. The only "change" is a fix for an obscure (potential crash) bug that may have been triggered when debug mode is turned on (/operserv set debug on) and someone tried to register a nickname. This version still requires MySQL. I'm working on the next version that will have a few new features as well as an entire storage subsystem to work on networks that don't use/want to use MySQL.
The interim 1.0.6 version can be found at
http://www.anthrochat.net/anopemodules/The completely volatile, always changing, development version (1.1.x) can also be found there, but keep in mind that until the version reads "1.2.0", consider it highly experimental, prone to crashes, and missing whole parts of its functionality. As of this writing, for example, it is missing the entire disk storage subsystem, so you need to manually add every blacklisted domain any time the module is loaded (ie. when services restarts). A couple of useful features have been added and are functioning (with limited, basic testing), so you can look forward to using those in the release version. The features include:
List users by e-mail, searchable with regular expressions
Set a "max limit" per domain in the blacklist, in cases where you may want to allow only a few registrations from one domain (instead of blacklisting it entirely)
Once 1.2.0 is ready, I'll submit it to the official modules site as well as the above-mentioned location.