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How to check MX records of mail server

Sometimes Mail Servers administrators have problem with receiving mails. One of the first things to troubleshoot is the MX record of their mail server in DNS. We can do it by using many online services or by using simple tools like nslookup or dig. One thing to note dig is Linux utility, while nslookup can be found on both Windows and Linux systems.

MX stands for MailExchanger. MX records are used to define mail hosts for the domain.

Checking MX entries using nslokup

C:\>nslookup
Default Server: dsi-app-server.test.local
Address: 192.168.2.1

> set type=mx
> microsoft.com
Server: dsi-app-server.test.local
Address: 192.168.2.1

Non-authoritative answer:
microsoft.com MX preference = 10, mail exchanger = mail.messaging.microsoft.com
microsoft.com nameserver = ns5.msft.net
microsoft.com nameserver = ns3.msft.net
microsoft.com nameserver = ns4.msft.net
microsoft.com nameserver = ns1.msft.net
microsoft.com nameserver = ns2.msft.net
mail.messaging.microsoft.com internet address = 216.32.181.22
mail.messaging.microsoft.com internet address = 65.55.88.22
mail.messaging.microsoft.com internet address = 207.46.51.86
mail.messaging.microsoft.com internet address = 213.199.154.22
mail.messaging.microsoft.com internet address = 216.32.180.22
ns3.msft.net internet address = 213.199.161.77
ns4.msft.net internet address = 207.46.66.126
ns5.msft.net internet address = 65.55.226.140
ns1.msft.net internet address = 65.55.37.62
ns2.msft.net internet address = 64.4.59.173

Checking MX entries using dig

mob@mob-ubuntu:~$ dig  yahoo.com MX

; <<>> DiG 9.5.1-P2 <<>> yahoo.com MX
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 5431 ;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 0, ADDITIONAL: 11
;; QUESTION SECTION:
;yahoo.com. IN MX

;; ANSWER SECTION:
yahoo.com. 6667 IN MX 1 f.mx.mail.yahoo.com.
yahoo.com. 6667 IN MX 1 g.mx.mail.yahoo.com.
yahoo.com. 6667 IN MX 1 a.mx.mail.yahoo.com.
yahoo.com. 6667 IN MX 1 b.mx.mail.yahoo.com.
yahoo.com. 6667 IN MX 1 c.mx.mail.yahoo.com.
yahoo.com. 6667 IN MX 1 d.mx.mail.yahoo.com.
yahoo.com. 6667 IN MX 1 e.mx.mail.yahoo.com.

;; ADDITIONAL SECTION:
g.mx.mail.yahoo.com. 1621 IN A 206.190.53.191
g.mx.mail.yahoo.com. 1621 IN A 209.191.118.103
a.mx.mail.yahoo.com. 1209 IN A 67.195.168.31
b.mx.mail.yahoo.com. 1101 IN A 66.196.97.250
b.mx.mail.yahoo.com. 1101 IN A 66.196.82.7
c.mx.mail.yahoo.com. 1630 IN A 216.39.53.2
c.mx.mail.yahoo.com. 1630 IN A 216.39.53.3
d.mx.mail.yahoo.com. 1743 IN A 68.142.202.247
d.mx.mail.yahoo.com. 1743 IN A 209.191.88.247
e.mx.mail.yahoo.com. 411 IN A 216.39.53.1
f.mx.mail.yahoo.com. 1179 IN A 98.137.54.237

;; Query time: 8 msec
;; SERVER: 62.179.1.62#53(62.179.1.62)
;; WHEN: Fri Jun 19 13:43:56 2009
;; MSG SIZE rcvd: 337

It is important to remember that due to propagation times of DNS records, sometimes we have to wait up to 48 hours to propagate through internet. Instead of using default name server, we can query specific DNS server when using both nslookup and dig.

nslookup example

C:\>nslookup

> server 62.179.1.62
Serwer domyślny: pl-waw4a-dns03.chello.pl
Address: 62.179.1.62

> set type=mx
> oracle.com
Serwer: pl-waw4a-dns03.chello.pl
Address: 62.179.1.62

Nieautorytatywna odpowied«:
oracle.com MX preference = 200, mail exchanger = acsinet12.oracle.com
oracle.com MX preference = 200, mail exchanger = acsinet11.oracle.com
oracle.com MX preference = 200, mail exchanger = rcsinet12.oracle.com
oracle.com MX preference = 200, mail exchanger = rcsinet11.oracle.com

acsinet11.oracle.com internet address = 141.146.126.233
rcsinet12.oracle.com internet address = 148.87.113.124
rcsinet11.oracle.com internet address = 148.87.113.123
acsinet12.oracle.com internet address = 141.146.126.234

dig example

mob@mob-ubuntu:~$ dig @62.179.1.62 oracle.com MX

; <<>> DiG 9.5.1-P2 <<>> @62.179.1.62 oracle.com MX ; (1 server found) ;; global options: printcmd ;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 55867 ;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 4

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

;; ANSWER SECTION:
oracle.com. 8153 IN MX 200 acsinet11.oracle.com.
oracle.com. 8153 IN MX 200 rcsinet12.oracle.com.
oracle.com. 8153 IN MX 200 rcsinet11.oracle.com.
oracle.com. 8153 IN MX 200 acsinet12.oracle.com.

;; ADDITIONAL SECTION:
rcsinet12.oracle.com. 2908 IN A 148.87.113.124
rcsinet11.oracle.com. 3576 IN A 148.87.113.123
acsinet12.oracle.com. 2428 IN A 141.146.126.234
acsinet11.oracle.com. 3696 IN A 141.146.126.233

;; Query time: 9 msec
;; SERVER: 62.179.1.62#53(62.179.1.62)
;; WHEN: Fri Jun 19 13:59:20 2009
;; MSG SIZE rcvd: 196

Online services

If you are finding it hard to use nslookup or dig, you can always use website, which will perform MX lookup for you. The one I would recommend is http://www.mxtoolbox.com/

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