Mike has suggested excluding certain domains; I think he said he thinks he
can narrow down a high percentage of the spam coming from a small number of
offending domains.  Therefore, I suggest a two-step remedy, going to the 2nd
only if the 1st doesn't work (well enough):

   1.  Mike filters off his list of offending domains.  (He could update his
filters over time.)
   2.  We close the list.

I don't want to go directly to #2 because I think we have just enough
inquiries from new Ada folks (i.e., non-subscribers) that this would work to
our community's disadvantage.