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3. MX
The MX can precede the mail transfer by the DNS search. If user want to change the mail server, then he
only need to modify the DNS record, in other words, the destination mail server has no need to know which
mail server that the user used to transfer mails.
Example 3：
T he MX r epr esen ts th e ma il e xch an ge ; it is a k ind o f DNS r ecord use d to pro vid e th e e- ma il
ser vic e.
If we type
nslookup -type=MX
strings after -type represents the DNS record. The mail.test.net.tw is the searched DNS host name which
mapped to the host25.test.net.tw mail exchange and it also mapped to the IP address of 211.22.22.24.
We assume th a t tes t Cus tomer Ser vice C en ter se nds th e e- ma il to
T he C us t om er Ser v ice p eo pl e s e nd th e mai ls th r ou gh t h e t es t .com . tw ( S MTP S er ver ) , a nd
t h e SM T P S er v er w i ll ask m ai l . tes t .n e t . tw o f w hic h w a y t o s e nd ma i ls v ia t he D N S s ea r c h .
The way to search th e MX record in mail .tes t.net.tw. ：
T he ma il se r ver o f ma i l .tes t.n e t.tw w il l se nd e-m ai ls to the a ddress o f host3.test.net.tw via
SMTP Protocol.
Host Name
host25.test.net.tw
mail.test.net.tw
The MX mapped relations
mail.test.net.tw
in DOS.（The nslookup is the DNS search command, and the
Host Name
host3.test.net.tw
mail.test.net.tw
The way to search the MX record in mail.test.net.tw
CS-2000 UTM Content Security Gateway User's Manual
Type
Address
A
211.22.22.24
MX
host25.test.net.tw
Type
Address
A
61.11.11.10
MX
host3.test.net.tw
- 464 -
mary@mail.tes t.net.tw
.
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