From: Wietse Venema (wietseporcupine.org)
Date: Wed Jan 31 2007 - 12:32:41 CST

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Victor Duchovni:
> On Wed, Jan 31, 2007 at 04:14:52PM -0200, Pedro Lamar?o wrote:
>
> > First off, I'm sorry to post this rather offtopic question.
> > I searched Google Groups for a USENET group specific to SMTP and found none.
> >
> > I've just read RFC 2487 and was left wondering exactly when is STARTTLS
> > allowed.
> > The obvious use case is to use it just after the TCP connection was
> > established, when the session is at the "initial" state.
> > But is it allowed after MAIL, when the session is at the "envelope" state?
> > Is it allowed after RCPT during the "envelope" state?
> > (This state terminology is mine, sorry if it is too confusing; I'm
> > trying to build a "state machine" picture out of the protocol.)
> >
> > The RFC merely states that, after STARTTLS handshaking completes, the
> > connection goes back to the "initial" state and a HELO or EHLO must be
> > issued.
>
> With SMTP, "STARTTLS" is allowed only between "EHLO" and "MAIL",
> and only if the server's ESMTP EHLO response includes "250-STARTTLS"
> (or ends with "250 STARTTLS").

A specific pointer would help. If you look at Postfix source, then
you will see that it accepts "STARTTLS" at any protocol stage,
except after "STARTTLS". Postfix accepts "STARTTLS" is accepted
after MAIL FROM, just like RSET, HELO or EHLO, because like Pedro
I could not find a statement to the contrary.

        Wietse

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