Le 25/10/2010 18:20, Leonardo Rodrigues a écrit :
Hi,
This question is not postfix-related .... so its somehow
off-topic. But it's related to mail systems, so i cant imagine any
other place to get some help on this subject.
I have a domain (domain.com.br) with lots of subdomains in the
format nnn.domain.com.br.
nnn.domain.com.br (about 40 different subdomains) have only 2
(two) DNS entries:
nnn IN MX 10 server.nnn.domain.com.br.
nnn IN TXT "v=spf1 include:domain.com.br -all"
there's absolutely no A entries for the subdomains.
i'm having an isolated problem with a customer that cannot send
mails to one of my subdomains (everything else is working fine,
several thousand of messages flowing daily, this really seems to be an
isolated problem). Altough, their sysadmin (from the domain which
cannot send us mail) is telling what i'm doing (having an MX entry but
no A entries) is RFC-illegal, altough he cannot point me which RFC i'm
not complaining with.
i really dont know if this setup (MX record but no A record) is
RFC-OK. The only think i know is that it's been working for years and
i receive thousand of emails daily on my several subdomains with no
problem at all.
question is .... do a domain (or in my case, a subdomain) *MUST*
have an A record ? Is the config i'm doing (DNS speaking) correct or
incorrect (RFC-speaking) ??
to receive email, you need either an MX OR an A record. you do not need
both.
Obviously, Wietse has no problem receiving email:
$ host -t a porcupine.org
porcupine.org has no A record
$ host -t mx porcupine.org
porcupine.org mail is handled by 10 spike.porcupine.org.
$ host -t a spike.porcupine.org.
spike.porcupine.org has address 168.100.189.2
nor do I (for @ml.netoyen.net):
$ host -t a ml.netoyen.net
ml.netoyen.net has no A record
$ host -t mx ml.netoyen.net
ml.netoyen.net mail is handled by 10 tichka.netoyen.net.
$ host -t a tichka.netoyen.net
tichka.netoyen.net has address 91.121.33.217
while many domains have an A record, this is related to the web, not
smtp. it's just so that http://example.com/ works (for mobile devices,
"www." is 4 chars...).
Anyway, the "common" way to configure MX servers is
example.com. MX 10 joe.example.org.
joe.example.org. A 192.0.2.1
that is
- the domain has an MX record which is a "hostname"
- that hostname has an A record
