Understanding of MX records in DNS

Understanding of MX records in DNS-Linux Enterprise Application-Linux server application information. The following is a detailed description. DNS uses MX records for mail routing. It specifies that the mail server of the domain name either processes or forwards emails related to the domain name. A forward mail is sent to an individual associated with the address. A forward mail is sent to its final destination through SMTP protocol. to prevent mail routing, the MX record has a special parameter besides the Domain Name of the email exchanger: Priority value. the priority value is an unsigned integer from 0 to 65535, which gives the priority of the email exchanger.
The priority value itself is not important. The key lies in its relative size with the priority value of other mail exchangers. The smaller the priority value, the higher the priority. emails are always first transmitted to the email exchanger with the smallest priority value. attempt to pass to a mail exchanger with a higher priority value after the failure. an email is always sent to an email exchanger with the same priority.

Note that hosts listed as email switches must have address records.

The following lists the records I have queried using the nslookup program:
Lee @ work :~ $ Nslookup
> Set type = mx
> Hnby.com.cn
Server: 10.10.16.60
Address: 10.10.16.60 #53

Non-authoritative answer:
* ** Can't find hnby.com.cn: No answer // No email exchange

Authoritative answers can be found from:
Hnby.com.cn
Origin = dns.hnby.com.cn
Mail addr = root.hnby.com.cn
Serial = 2002120101
Refresh = 900.
Retry = 600.
Expire = 86400
Minimum= 3600
> Set type = mx
> Henan.gov.cn
Server: 10.10.16.60
Address: 10.10.16.60 #53

Non-authoritative answer:
* ** Can't find henan.gov.cn: No answer

Authoritative answers can be found from:
Henan.gov.cn
Origin = ns.hazzptt.net.cn
Mail addr = root.ns.hazzptt.net.cn
Serial = 99968011
Refresh = 28899.
Retry = 7200.
Expire = 604800
Minimum= 86400
> Set type = mx
> Yahoo.com.cn
Server: 10.10.16.60
Address: 10.10.16.60 #53

Non-authoritative answer:
Yahoo.com.cn mail exchanger = 10 mta-v1.mail.vip.cnb.yahoo.com. // Yahoo China mail exchange service

Authoritative answers can be found from:
Yahoo.com.cn nameserver = ns8.yahoo.com.
Yahoo.com.cn nameserver = ns9.yahoo.com.
Yahoo.com.cn nameserver = ns1.yahoo.com.
Yahoo.com.cn nameserver = ns3.yahoo.com.
Yahoo.com.cn nameserver = ns6.yahoo.com.
Ns1.yahoo.com internet address = 66.218.71.63
Ns3.yahoo.com internet address = 217.12.4.104
Ns6.yahoo.com internet address = 202.43.223.170
> Set type = mx
> Yahoo.com
Server: 10.10.16.60
Address: 10.10.16.60 #53

Non-authoritative answer:
Yahoo.com mail exchanger = 1 mx3.mail.yahoo.com.
Yahoo.com mail exchanger = 1 mx1.mail.yahoo.com.
Yahoo.com mail exchanger = 1 mx2.mail.yahoo.com.

Authoritative answers can be found from:
Yahoo.com nameserver = ns1.yahoo.com.
Yahoo.com nameserver = ns2.yahoo.com.
Yahoo.com nameserver = ns3.yahoo.com.
Yahoo.com nameserver = ns4.yahoo.com.
Yahoo.com nameserver = ns5.yahoo.com.
Mx3.mail.yahoo.com internet address = 4.79.181.12
Mx3.mail.yahoo.com internet address = 67.28.113.10
Mx3.mail.yahoo.com internet address = 4.79.181.168
Mx3.mail.yahoo.com internet address = 4.79.181.134
Mx3.mail.yahoo.com internet address = 67.28.113.74
Mx1.mail.yahoo.com internet address = 67.28.113.71
Mx1.mail.yahoo.com internet address = 67.28.113.73
Mx1.mail.yahoo.com internet address = 67.28.113.19
Mx1.mail.yahoo.com internet address = 4.79.181.14
Mx1.mail.yahoo.com internet address = 4.79.181.15
Mx1.mail.yahoo.com internet address = 4.79.181.168
Mx2.mail.yahoo.com internet address = 4.79.181.135
Mx2.mail.yahoo.com internet address = 4.79.181.136
Mx2.mail.yahoo.com internet address = 4.79.181.168
Mx2.mail.yahoo.com internet address = 67.28.113.70
Mx2.mail.yahoo.com internet address = 67.28.113.72
Ns1.yahoo.com internet address = 66.218.71.63
Ns2.yahoo.com internet address = 66.163.169.170
Ns3.yahoo.com internet address = 217.12.4.104
Ns4.yahoo.com internet address = 68.142.196.63
> Set type = mx
> Dahedomaincom.cn
Server: 10.10.16.60
Address: 10.10.16.60 #53

* ** Can't find dahew.com.cn: No answer
> Set type = mx
> Dahedomaincom
Server: 10.10.16.60
Address: 10.10.16.60 #53

Non-authoritative answer:
Dahew.com mail exchanger = 10 mail1.dahew.com.

Authoritative answers can be found from:
Dahew.com nameserver = ns1.dns-diy.com.
Dahew.com nameserver = ns2.dns-diy.com.
Mail1.dahew.com internet address = 219.156.123.177
Ns1.dns-diy.com internet address = 210.51.187.81
Ns1.dns-diy.com internet address = 218.16.225.50
Ns1.dns-diy.com internet address = 60.191.252.66
Ns2.dns-diy.com internet address = 218.107.207.123
Ns2.dns-diy.com internet address = 218.85.134.143
Ns2.dns-diy.com internet address = 64.84.29.59


When we configure bind, make the following statement:
$ TTL 3 h

@ SOA my.test.com. root.test.com .(
; ^
;
2000020501; serial number
3 h; Refresh after 3 hours
1 h; 1 hour later.
1 w; 1 week late full
1 h) No cache TTL is 1 hour


There is a difference between them, @ In the SOA type Record Name field, it refers to the current source, it is test.com

Ns in ns.test.com.
; Name Server
Mx in 10 mx.myhome.com.
; Email server
Ns.myhome.com. in a 192.168.1.1
Mx.myhome.com. in a 192.168.1.1

Things can be truly understood only after they are seen. Scientific and rational spirit, but the actual operation must be empirical!