When I enter:
     TELL LISTSERV   SHOW ALIAS PTEARN
LISTSERV fetches the ":internet" tag, and send me the response:
   * Node PTEARN is also known as PTEARN.FCL.PT.
However, when I ask NSLOOKUP for the Internet address for this name,
I get an authoritative "non-existent domain" error message from 'NS.DNS.PT'.
Can anyone explain why?
 
P.S. When I ask NSLOOKUP for the address for 'PTEARN.FC.UL.PT',
     i.e., a slight-different name, it reports '192.68.221.1'.
 
P.P.S. Similarly, 'PTIFM.IFM.PT' and 'PTIFM.IFM.RCCN.PT' are equally-confusing!