
Even more interesting: the SMTP server at csrc.ncsl.nist.gov no longer
recognizes the 'expn' and 'vrfy' commands...

   telnet csrc.ncsl.nist.gov smtp
   Trying 129.6.54.11...
   Connected to csrc.ncsl.nist.gov.
   Escape character is '^]'.
   220 first.org sendmail 4.1/NIST ready at Tue, 20 Apr 93 17:01:34 EDT
   expn clipper
   500 Command unrecognized

Seems like sombody didn't like your snooping around, Marc.