If the LISTSERV host is on the Internet, you can generally (try
to) do a:
 
TELNET hostname 25
 
(in LINE mode, not VTxxx or TN3270).
 
You should be rewarded within one minute with a one-line
banner.  Your proper ressponse to that should be the single
line command
 
QUIT
 
If you did not get the banner within that minute, you need
to terminate the TELNET session (you should know how do that
BEFORE you initiate the command).  Not getting the banner
probably means that the LISTSERV host isn't available for
any one of a number of reasons -- some already enumerated.
 
--  co-owner INFOSYS, TQM-L, CPARK-L, ERAPPA-L, JANITORS, LDBASE-L, et -L
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