From: Noel Jones (njonesmegan.vbhcs.org)
Date: Tue Apr 13 2010 - 10:44:44 CDT

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On 4/13/2010 2:16 AM, Bob Eastbrook wrote:
> I use wildcard MX records for mail, and a wildcard CNAME for web
> traffic. For example:
>
> *.example.com = MX record for mail.example.com
> *.example.com = CNAME myapp.appspot.com

MX records must not point to a CNAME.

>
> Email to bobfoo.example.com gets delivered to mail.example.com, and
> web traffic to http://foo.example.com goes to myapp.appspot.com. I
> use instructions from Wietse from a post I made on Dec 31, 2009:
> http://www.pubbs.net/200912/postfix/75444-virtual-domains-for-wildcard-mx-records.html.
>
> This works for all mailers I've found except for Yahoo Mail. Mail
> sent from Yahoo is rejected with:
>
> <bobfoo.example.com>:
> [ip.number.of.mailserver] does not like recipient.
> Remote host said: 554 5.7.1<bobmyapp.appspot.com>: Relay access denied
> Giving up on [ip.number.of.mailserver].

Original RFC822 said that mail to a CNAME should be rewritten
to the canonical name. Later RFC's relaxed that, but some
mailers still behave that way.

Don't use a CNAME for email. That will fix the problem.

   -- Noel Jones

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