On Thu, 6 Feb 2003, Vadim Vygonets wrote:
> Versions of Postfix older than 2.0.0.1 (2002-12-09) seemed to
> rewrite the recipient address if the domain part is a CNAME
> record in the DNS,
Rewriting to the canonical name was the fashion - and the requirement -
in the early days. This is from RFC 1123:
5.2.2 Canonicalization: RFC-821 Section 3.1
The domain names that a Sender-SMTP sends in MAIL and RCPT
commands MUST have been "canonicalized," i.e., they must be
fully-qualified principal names or domain literals, not
nicknames or domain abbreviations. A canonicalized name either
identifies a host directly or is an MX name; it cannot be a
CNAME.
This requirement was carried out by some MTAs, and ignored by others. It
has been dropped in 2821; there is no longer any mention of "canonical"
names.
> And some more questions: do any MTAs except the older Postfix
> rewrite recipient addresses based on CNAME records?
I believe that Sendmail used to, but I don't know if it still does, or
when it changed, if it did.
> Honestly, it seems to me like a brain-dead idea pulled out of a bodily
> orifice not normally mentioned in polite circles, but I'm prepared to
> be shown the light if I'm mistaken.
It was felt to be a good idea at the time. People were thinking in terms
of individual hosts and their (single) email domain. CNAMEs were
intended just to be alternative names for the same thing. All the
virtual stuff came later.
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
