6

I've been reading this: http://www.zytrax.com/books/dns/ch8/mx.html

For MX records, and I've setup my nameserver via bind. Here is my zonefile for my website:

$TTL 86400
@   IN  SOA     ns1 root (
        2           ;Serial
        3600        ;Refresh
        1800        ;Retry
        604800      ;Expire
        86400       ;Minimum TTL
)
; Specify our two nameservers
        IN  NS      ns1
        IN  NS      ns2

; Nameserver resolve
ns1     IN  A       1.1.1.1
ns2     IN  A       2.2.2.2

; Mail server
        IN  MX 10   mail

; Hostnames
@       IN  A       2.2.2.2
www     IN  A       2.2.2.2
mail    IN  A       1.1.1.1

I am hosting postfix and dovecot. I am unable to receive emails remotely and I've narrowed it down to my DNS not responding correctly on MX requests.

Dovecot and postfix are both hosted on 1.1.1.1 (I've changed my server IP)

After changing my config and restarting bind, 

dig example.com MX @localhost

EDIT: I've tried both mail.example.com and example.com. Both failed. I've updated this question for example.com as I initially posted the dig for mail.example.com (this was an error on my part. It has been updated, though.)

To which I receive,

;; QUESTION SECTION:
;example.com.              IN      MX

;; AUTHORITY SECTION:
example.com.            86400   IN      SOA     ns1.example.com. root.example.com

;; Query time: 0 msec
;; SERVER: ::1#53(::1)
;; WHEN: Thu Jul  3 15:29:40 2014
;; MSG SIZE  rcvd: 79

EDIT: Thought I'd include that everything else works fine. I.e. www.example.com

Jason
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3 Answers3

16

A really tricky configuration error. By starting a line with neither a hostname, the zone name or the @ shorthand for the zone origin, becomes a continuation of the record above. 

ns2     IN  A       2.2.2.2
; Mail server
        IN  MX 10   mail.example.com.

is actually 

ns2     IN  A       2.2.2.2
; Mail server
ns2     IN  MX 10   mail.example.com.

and not what you intended:

ns2     IN  A       2.2.2.2
; Mail server
example.com.      IN  MX 10   mail.example.com.

or alternatively you should have used:

@      IN  MX 10   mail.example.com.
HBruijn
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  • Thanks. I didn't know that. It explains why it didn't work though. I've simply moved my MX record and placed it under the NS records. It works fine now. – Jason Jul 03 '14 at 19:52
  • Yes at that location it is the fourth record for the origin ; `SOA`, two `NS` records and then the `MX` record. – HBruijn Jul 03 '14 at 19:54
2

I think you're missing a dot. It should read

IN  MX 10   mail.example.com.

or

IN  MX 10   mail

Otherwise it will be relative to your zone, i.e. results in mail.example.com.example.com..

I'm not sure if this is really the problem but give it a try.

Mario Lenz
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  • Yes. when the question was posted it was missing a dot. I updated it really fast once I noticed this and tested it again (I restarted bind). It still doesn't work. I'm going to try it again with mail and reply with my result. EDIT: `IN MX 10 mail` still doesnt work. – Jason Jul 03 '14 at 19:41
1

If you don't change the serial number of your zone file, it will not update anything.

There is already a question on SF regarding the importance of serial number in DNS zone files: DNS records serial number

After re-reading your zone, I believe your MX is not properly "declared".

it should read

example.com. MX 10 mail.example.com.
Community
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Alex
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  • I've changed the serial number to 2 and am now using `IN MX 10 mail`. I restarted my bind service but I still get the same response from dig. – Jason Jul 03 '14 at 19:43
  • Serial number shouldn't have mattered in this case since he's directly querying the DNS sever (localhost). It is relevant when propagating though. – Belmin Fernandez Jul 04 '14 at 01:01