One has to admire these spammers :(

[Arnt Gulbrandsen <agulbra@troll.no>]

I just now got a spam to <>.  AFAIK, <> is legal only as a source
address, not a destination address, but I got it.  (A quick check
shows that zmailer and qmail both say 250 on RCPT TO: <>, sendmail
says 550.)

So, I hacked my smtpcmds.c to outlaw it - a trivial change to
smtpcmds.c - and would like some advice.  Would it be better to do
this in the router?  And when I think that <> is illegal as
destination, am I forgetting my RFCs again?  Matti, do you want the
patch?

(I wonder how long it'll take before someone traverses the entire DNS
and sends spam to all@<x> for -all- valid <x>.)

--Arnt