I'm quite happy to acknowledge and accept corrections like this! Thanks for the info.
...Todd On Mon, Sep 9, 2013 at 10:04 AM, Viktor Dukhovni <[email protected]> wrote: > On Mon, Sep 09, 2013 at 09:00:01AM -0700, Todd Lyons wrote: > >> > > [email protected] >> > > <-- [email protected] >> >> I think it's a terminology issue. It's not exim "rewriting" the email >> address. I believe a more technically correct phrase would be >> "normalizing". A domain is not supposed to have an MX record set to a >> CNAME. > > You're mistaken. The illegal configuration is: > > example.com. IN MX 0 mail.example.com. > mail.example.com. IN CNAME smtp.example.com. > smtp.example.com. IN A 192.0.2.1 > > However, the below (which is the OP's situation) is valid (since > April 2001, RFC 2821): > > example.com. IN CNAME example.net. > example.net. IN MX 0 smtp.example.net. > smtp.example.net. IN A 192.0.2.1 > > More than a decade ago (prior to RFC 2821), envelope recipient > addresses of the form [email protected] (with example.com as > above) were expected to be canonicalized (normalized if you will) > to [email protected] since RFC 821 requires primary names in > all contexts where domains are used. This was relaxed in RFC 2821 > with the express purpose of allowing <[email protected]> in > MAIL FROM: and RCPT TO:. > > MTAs are now expected to not automatically canonicalize the domain > part of envelope recipient addresses based on the presence of a > DNS CNAME alone. Of course explicit rewriting rules in the MTA > configuration can rewrite local addresses at will, and remote > addresses at their peril. > >> Behavior when such an event occurs is undefined. Some MTA's >> merely fix the sending domain from the (invalid) CNAME to the >> (standards compliant) A record. I *know* sendmail does this as I'm a >> list owner on a mailing list machine which has this particular >> configuration. Read on for exim behavior in this scenario: > > Sendmail (in best-practice and default configurations) no longer > automatically canonicalizes the domain part of envelope recipient > addresses. The same is true of Postfix. > >> Yes it has been changed, but no it's not incorrect (IMHO). > > Your opinion is contrary to long established standards. > > -- > Viktor. > > -- > ## List details at https://lists.exim.org/mailman/listinfo/exim-dev Exim > details at http://www.exim.org/ ## -- The total budget at all receivers for solving senders' problems is $0. If you want them to accept your mail and manage it the way you want, send it the way the spec says to. --John Levine -- ## List details at https://lists.exim.org/mailman/listinfo/exim-dev Exim details at http://www.exim.org/ ##
