MX records and CNAME records for DNS

The MX record is the mapping of the mail domain to the mail server (domain name). can be mapped to multiple mail servers, and a send will be selected when sent.

After you get the new domain name, you also need to look for DNS, turn the domain name to no IP

Original: http://my.oschina.net/u/1382972/blog/340273

MX record

The mail exchanger RECORD,MX record the server address of the domain name that was sent when the e-mail message occurred. E-mail is sent using the SMTP Application layer protocol.

For example, to send mail to [email protected], where the domain name part of the QQ.COM,MX record describes the sending of e-mail should be sent to that server.

You can use the dig command to query MX records:

Dig qq.com mx

The output is:

; <<>> DiG 9.9.5-3-ubuntu <<>> qq.com mx

;; Global options: +cmd

;; Got Answer:

;; ->>header<<-opcode:query, Status:noerror, id:48801

;; Flags:qr Rd RA; Query:1, Answer:3, Authority:4, additional:1

;; OPT pseudosection:

; edns:version:0, Flags:; udp:4096

;; QUESTION section:

; qq.com. In MX

;; ANSWER section:

qq.com. 5864 in MX mx1.qq.com.

qq.com. 5864 in MX mx3.qq.com.

qq.com. 5864 in MX mx2.qq.com.

;; Authority section:

qq.com. 65518 in NS ns2.qq.com.

qq.com. 65518 in NS ns3.qq.com.

qq.com. 65518 in NS ns4.qq.com.

qq.com. 65518 in NS ns1.qq.com.

;; Query time:88 msec

;; server:127.0.0.1#53 (127.0.0.1)

;; When:mon Nov 16:53:27 CST 2014

;; MSG SIZE rcvd:167

MX records from left to right parts of the meaning:

Example qq.com. 5864 in MX mx1.qq.com.

1, the corresponding domain name, here is qq.com., '. ' Represents the root domain, COM top-level domain name, QQ level two domain name

2, Ttl,time ro live, cache time, unit seconds. 5864, which represents the cache name server, which can be saved in the cache for 5,864 seconds.

3, class, to query the category of information, in the category for the IP protocol, that is, the Internet. There are other categories, such as chaos, because it is now the Internet, so the other basic use.

4, type, record type, MX record, represent this record as MX record

5, preference number priority, the value is custom by the domain manager, the smaller the value the higher the priority. For example, here are 3 MX records, each corresponding to the priority 30\10\20. The e-mail sending software can select the appropriate server based on the priority values in the returned MX.

6. mx1.qq.com. The server address that should be used to send the message. Because it is still a domain name, further DNS queries are required to obtain its IP address.

CNAME record

The Canonical name Record,cname record specifies that the domain name is an alias for another official domain name (Canonical name).

Many websites use the CDN Acceleration feature to take advantage of this record.

For example, using the dig command to query the new Caixin Network (http://caixin.com/) images used in the domain name, in the results see the CNAME record trace:

Dig img.caixin.com

The result of the output is:

; <<>> DiG 9.9.5-3-ubuntu <<>> img.caixin.com

;; Global options: +cmd

;; Got Answer:

;; ->>header<<-opcode:query, Status:noerror, id:13265

;; Flags:qr Rd RA; Query:1, Answer:8, Authority:8, Additional:9

;; OPT pseudosection:

; edns:version:0, Flags:; udp:4096

;; QUESTION section:

; img.caixin.com. In A

;; ANSWER section:

Img.caixin.com. In CNAME img.caixin.ccgslb.com.cn.

img.caixin.ccgslb.com.cn. 1762 in CNAME webcache.foreign.ccgslb.com.

webcache.foreign.ccgslb.com. 209.177.81.12 in A

webcache.foreign.ccgslb.com. 180.210.229.37 in A

webcache.foreign.ccgslb.com. 65.255.44.2 in A

webcache.foreign.ccgslb.com. 209.177.81.134 in A

webcache.foreign.ccgslb.com. 209.177.81.136 in A

webcache.foreign.ccgslb.com. 209.177.81.141 in A

;; Authority section:

ccgslb.com. 668 in NS ns8.ccgslb.com.

ccgslb.com. 668 in NS ns9.ccgslb.com.

ccgslb.com. 668 in NS ns17.ccgslb.com.

ccgslb.com. 668 in NS ns18.ccgslb.com.

ccgslb.com. 668 in NS ns19.ccgslb.com.

ccgslb.com. 668 in NS ns20.ccgslb.com.

ccgslb.com. 668 in NS ns21.ccgslb.com.

ccgslb.com. 668 in NS ns22.ccgslb.com.

;; ADDITIONAL section:

ns8.ccgslb.com. 65022 in A 58.68.168.123

ns9.ccgslb.com. 66818 in A 118.98.102.122

ns17.ccgslb.com. 78032 in A 180.210.229.54

ns18.ccgslb.com. 78308 in A 119.188.140.75

ns19.ccgslb.com. 78032 in A 209.177.90.31

ns20.ccgslb.com. 78075 in A 180.210.234.20

ns21.ccgslb.com. 78075 in A 23.236.126.17

ns22.ccgslb.com. 16524 in A 122.228.86.69

;; Query time:179 msec

;; server:127.0.0.1#53 (127.0.0.1)

;; When:mon Nov 17:29:26 CST 2014

;; MSG SIZE rcvd:493

You can see two CNAME records from the results:

Img.caixin.com. In CNAME img.caixin.ccgslb.com.cn.

img.caixin.ccgslb.com.cn. 1762 in CNAME webcache.foreign.ccgslb.com.

The records have the same meaning as a record:

1, the corresponding domain name, here is img.caixin.com., '. ' Represents root domain, COM top-level domain name, Caixin two domain name, IMG is level three domain name

2, Ttl,time ro live, cache time, unit seconds. 30, which represents the cache name server, which can be saved in the cache for 30 seconds.

3, class, to query the category of information, in the category for the IP protocol, that is, the Internet. There are other categories, such as chaos, because it is now the Internet, so the other basic use.

4, type, record type, CNAME record, represent this record as CNAME record

5, img.caixin.ccgslb.com.cn. Is the domain name img.caixin.com. is the alias (alias) of the official domain name (Canonical name).

Ccgslb.com.cn is the domain name used by the CDN company ChinaCache. When you visit a picture of the Caixin network, you will use the accelerator service of the CDN company.

MX records and CNAME records for DNS (RPM)