--On Thursday, 12 April, 2007 19:08 +0100 Tony Finch
ehlo = "EHLO" SP ( Domain / Explained-literal
Explained-literal = address-literal [string]
Um, boggle. Why was this new syntax introduced? Clients that
use it are going to fail to negotiate ESMTP even though both
the client and the server support it, because existing servers
(sendmail, exim, exchange) will reject it as an error. This
new feature is also incomplete - there's no syntax for
including the string explanation in a Received: trace field.
This was introduced after a lengthy discussion that, according
to my notes, occurred in late 2003. I apparently sent a note to
this list confirming it on 20040103. The issue is discussed
early in 184.108.40.206 and has to do with the desire to permit the
client to attach some free text explaining why a literal is
being used rather than a domain name.
I'm happy to assign an issue number if others believe the
decision needs revisiting.