The development that led to RFC1893 was known as "Notary". The drafts had
names like "notary-mime-delivery-07", the thing was generally known to
the people who run mail systems as "notary" and it was just a draft at
the time LISTSERV added support for it (1893 didn't exist, etc). Now that
it is a standard, I should probably replace this word with "DSN" or
"RFC1893". I have no idea why the working group chose this name.
Eric