[zagaberoo]

I wonder how effective it would be to look up the MX record of each domain (or just the A record, as it looks like all of mailinator's alternate domains have MX records that just point to their own A records) and ban based on the IP address? You'd have to update periodically, I suppose, but all of mailinator's alternate domains resolve to the same IP address. Of course it seems to be a moot point nowadays.