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
<viktor1dane@???> wrote:
> On Mon, Sep 09, 2013 at 09:00:01AM -0700, Todd Lyons wrote:
>
>> > > nonesuch@www.bcidahofoundation.com
>> > > <-- nonesuch@???
>>
>> 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 localpart@??? (with example.com as
> above) were expected to be canonicalized (normalized if you will)
> to localpart@??? 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 <user@???> 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
