MX record and MX record priority

Source: Internet
Author: User
Tags mail exchange mx record nameserver nslookup

MX record and MX record priority
Mx (Mail exchanger) Record
A mail exchange Record pointing to an email server. It is used to locate the email server based on the recipient's address suffix when the email system sends an email. For example, when a user on the Internet wants to send a letter to a user@mydomain.com, the user's email system looks for the MX record for the domain name mydomain.com through DNS, if the MX record exists, the user's computer sends the email to the email server specified by the MX record.
Methods for checking the existence of MX records
A very useful tool for DNS query is NSlookup, which can be used to query various data in DNS. You can directly run NSLookup in Windows command line to enter an interactive mode, where you can query various types of DNS data.
DNS name resolution data can be of different types, including the SOA type data with the parameter set for this zone, and the type data with the IP address corresponding to the parameter set for this zone, there is MX data set for mail exchange. These different types of data can be queried through the NSLookup interactive mode. During the Query Process, you can use the set type command to set the corresponding Query type.
For example:
C:/Documents and Settings/Administrator> NSLookup
Default Server: a.center-dns.jsinfo.net
Address: 218.2.135.1

> Set type = mx
> Sohu.com
Server: a.center-dns.jsinfo.net
Address: 218.2.135.1

non-Authoritative Answer:
sohu.com MX preference = 5, mail exchanger = sohumx1.sohu.com
sohu.com MX preference = 10, mail exchanger = sohumx.h.a.sohu.com

Sohu.com nameserver = ns2.sohu.com
Sohu.com nameserver = ns1.sohu.com
Sohu.com nameserver = dns.sohu.com
Sohumx1.sohu.com Internet address = 220.181.26.202
Ns2.sohu.com Internet address = 220.181.26.167
Dns.sohu.com Internet address = 61.135.150.76
Ns1.sohu.com Internet address = 61.135.179.169
If the MX record of a domain name does not exist, a message similar to the following appears:
> 71mc.net
Server: a.center-dns.jsinfo.net
Address: 218.2.135.1

* ** A.center-dns.jsinfo.net can't find 71mc.net: non-existent domain
You can also use commands such as nsloolup-Qt = mx 71mc.net to query the MX records of 71mc.net.

MX priority is meaningless when only one MX record exists.

the smaller the MX number value, the higher the priority. The same domain name has two MX records with different priorities, usually with a higher priority. When a machine with a higher priority cannot be used, a lower priority can be used for temporary backup, receiving emails and forwarding. When a machine with a higher priority is normal, the lower level will attempt to forward the mail to the server with a higher priority.

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