> I'm starting a new list and I want to send a welcome message to new
> subscribers. How do I do that?

Send the following message (appropriately modified) to your LISTSERV:
-8<-------------------------------------------------------------------
put <listname> welcome pw=XXXXXXXX
Subject: Welcome to <listname>!
Lots of lines
of text
-8<-------------------------------------------------------------------

Replace the <listname> bit with the name of your list, obv.

HTH,

Paul