Some days ago, Stan (owner of HELP-NET) was asking about some
mysterious mail bounces from the Netherlands.  He had checked
his subscriber list, but hadn't found anyone at the system from
which the bounce messages originated.
 
Well.........the problem subscribers are there, but they're a
bit difficult to locate.
 
The DNS (Domain Name Service) software allows a site/domain
manager to specify a *lot* of information; it also allows a
*very* customized setup.  One of the resources available in
DNS is the MX (Mail eXchanger) record; it allows the dynamic
routing of email to a given hub system.  For instance, email
to anyone in my domain (engr.uky.edu) is directed to our mail
hub system, d.ecc.engr.uky.edu, with an MX record.
 
I pulled down the subscriber list to HELP-NET, extracted the
addresses in the Netherlands, and asked the nameserver if any
MX records existed for those domain addresses.  Lo and behold:
 
     CARPEDM.HACKTIC.NL.        86337   MX      200 sun4nl.nluug.nl.
     CC.RUU.NL.                 86337   MX      100 sun4nl.nluug.nl.
     GALILEO.NL.                345541  MX      100 sun4nl.nluug.nl.
     GWDCAF.DWG.RWS.NL.         345542  MX      100 sun4nl.nluug.nl.
 
HELP-NET has subscribers in each of these domains; their email is
routed, at times, through sun4nl.nluug.nl.  Look to the postmasters
at these sites for help.
 
--Wes
 
ps> If you have access to the TCP/IP Internet, you might want to
    play with 'dig' -- it's a public domain piece of software that
    lets you interrogate the nameservers for all kinds of useful
    information.  If you have access to the Unix nslookup(1) com-
    mand, it will do the same things (but in a much more kludgy
    fashion)......