Subject: smtpupd-09 and syntax checks

From: "D. J. Bernstein" <[email-masked]>
Date: 31 Jan 1999 00:09:34 -0000

Of the 50 most common SMTP server implementations on the Internet today,
every single one accepts a variety of syntax extensions; sometimes for
interoperability, sometimes simply for implementor convenience.

Of course, the client is violating RFC 821 if it uses these extensions.
But the _server_ is _not_ violating RFC 821. RFC 821 does not require
that servers reject syntax extensions.

smtpupd takes a different approach. Three examples, in direct conflict
with current practice:

   * Servers ``SHOULD'' reject 8-bit ``envelope commands.''
   * Servers ``SHOULD'' reject RSET BLAH BLAH BLAH.
   * Servers ``MUST'' reject HELO under_score.

Exactly what benefit are these changes supposed to have?

``Rejecting RSET BLAH BLAH BLAH will allow future extensions,'' we're
told. That's a specious argument. The standard extension method, using
new command names, is just as powerful, and has the huge advantage that
it doesn't demand changes from unextended servers. Nobody disputes this.

``There isn't consensus against the changes,'' we're told. But there
also isn't consensus _for_ the changes! The document editor is screwing
up the spec, trying to fight widespread practice, over objections from
several people. He is, as I said before, literally out of control.

---Dan