Computerized Horizons [sce-spf_discuss(_at_)declude(_dot_)com] wrote:
> CNAMEs and MX records are a very bad combination. There are at least 3
> ways that they can be combined, 2 of which are invalid, one is valid but
> may cause problems. So the best thing to do is not use the CNAME. I
> don't bother trying to remember which type is allowed -- your best bet,
> if you really want to keep the CNAME, is to go through the RFCs to
> figure out if the way you want to set it up is allowed.
gray:~> dig +noall +answer mehnle.net TXT|grep CNAME
mehnle.net. 43200 IN TXT "MX->CNAME is by intention. Go read
<http://www.mengwong.com/misc/rfc1912-is-wrong.html>."
Well, you've forced me to go to my master "MX and CNAME" notes. :)
[1] A domain with both a MX and CNAME record is illegal (such as
"example.com. CNAME example.net." and "example.com. MX 10 mail.example.net"
[2] A domain that has an MX query return a CNAME is illegal (such as
"example.com. CNAME example.net.")
[3] A domain that has the hostname in a MX response point to a CNAME may be
technically legal, but will be unstable (such as "example.com. MX 10
mail.example.com" and "mail.example.com. CNAME mail.example.net").
You are doing #3, so may be technically legal. However, there is a good
chance that some mailservers may not understand the situation (and a great
chance that testing tools and even spam tools will not understand the
situation).
-Scott
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