I get this question a lot, so I hope you don't mind my copying
html-wg on this reply.
By convention, mailing list administrivia for list@domain goes to
list-request@domain. If that is some sort of automated "mail robot,"
the human responsible is available as a last resort at
list-owner@domain.
The list in this case is sgml-internet@ebt.com. So send a
human-readable subscription request to
sgml-internet-request@ebt.com. You message might be received by a
human, but more likely, it will be received by some "mail robot"
software that will object to the syntax of your message for some
reason. It will very likely include detailed subscription instructions
in its reply.
Let me know if this proves not to be the case.
Dan