1
1
I have a domain, and that domain uses another one of my domains to handle mail. I'm having trouble getting it configured in a way to make all mail clients play well with my domains.
In terms of foo
and bar
, foo.com
is my "main" server:
foo.com
is my mail serverfoo.com
: MX record => IP Addressmail.foo.com
: MX record => IP Addressmail.foo.com
: A record => IP Address
And bar.com
is my domain that uses foo.com
:
bar.com
: MX record =>mail.foo.com
mail.bar.com
: MX record =>mail.foo.com
I cannot add the following for mail.bar.com
:
mail.bar.com
: CNAME record =>mail.foo.com
When I attempt to enter the CNAME record so some mail clients can connect via mail.bar.com
, I get an error:
Duplicate subdomains are not allowed between these record types: MX; CNAME
Essentially the error is saying I cannot have:
mail.bar.com
: MX record =>mail.foo.com
mail.bar.com
: CNAME record =>mail.foo.com
I don't quite understand the error messages because the resource records specify different services. Folks trying to send email to the domains will use the MX records; while folks trying to retrieve their email will use the CNAME record.
I looked at RFC 1035, but I do not see where the standard prohibits the combination. I also tried to follow some of the updated RFCs, but many of them did not apply to the base service implementation.
Are MX and CNAME mutually exclusive? If so, is there a reference somewhere?
Here's the related question: Can't configure account with Thunderbird (broken Mail Account Setup). Thunderbird refuses to allow me to create an account. I'm trying to tweak DNS by adding a CNAME to see if it helps.
1Couldn't you use an ALIAS record instead of a CNAME for the second mail.bar.com? I was under the impression that CNAME should only be used when there are no other existing records under that name. – JNevill – 2014-09-17T15:43:23.893
@JNevill - this is not web mail, so URL aliases won't be helpful. The server only offers SMTP, SMTPS, IMAPS and Secure-MSA. – jww – 2014-09-17T16:02:35.087
@JNevill - Re: "[use CNAME when] ... no other existing records". Yea, that worked for most clients. I added information on the underlying problem. – jww – 2014-09-17T16:10:03.000