[SOLVED] mx and email server

luofeiyu · 09-28-2017, 02:33 AM

An MX (Mail eXchange) record will redirect email sent to any user's machine to a designated mailhost.
It tells the MDA where to route email.
MX records point to an SMTP delivery service that receives email for the given domain.
It points to hosts that handle only smtp requests (which arrive at 25 tcp port by default).

Code:

dig 163.com -t mx
;; ANSWER SECTION:
163.com.		6212	IN	MX	10 163mx01.mxmail.netease.com.
163.com.		6212	IN	MX	10 163mx03.mxmail.netease.com.
163.com.		6212	IN	MX	50 163mx00.mxmail.netease.com.
163.com.		6212	IN	MX	10 163mx02.mxmail.netease.com.

dig 163mx01.mxmail.netease.com +short
220.181.14.136
220.181.14.142
220.181.14.138
220.181.14.135
220.181.14.143
220.181.14.140
220.181.14.139
220.181.14.137
220.181.14.141

dig 163mx00.mxmail.netease.com +short
123.125.50.139
123.125.50.140

dig 163mx02.mxmail.netease.com +short
220.181.14.155
220.181.14.154
220.181.14.150
220.181.14.144
220.181.14.148
220.181.14.145
220.181.14.147
220.181.14.149
220.181.14.146

dig 163mx03.mxmail.netease.com +short
220.181.14.160
220.181.14.161
220.181.14.159
220.181.14.158
220.181.14.157
220.181.14.162
220.181.14.164
220.181.14.163
220.181.14.156


dig  smtp.163.com  +short
123.125.50.133
123.125.50.138
123.125.50.134
123.125.50.135
123.125.50.132

Why none of them (163mx00.mxmail.netease.com and 163mx01.mxmail.netease.com and 163mx02.mxmail.netease.com and 163mx03.mxmail.netease.com) contain one of it in

123.125.50.133
123.125.50.138
123.125.50.134
123.125.50.135
123.125.50.132

Or to say, why the result is not as below?

Code:

dig 163.com -t mx
;; ANSWER SECTION:
163.com.        6212    IN  MX  10  123.125.50.133
163.com.        6212    IN  MX  10  123.125.50.138

TenTenths · 09-28-2017, 06:10 AM

Quote:

Originally Posted by luofeiyu

An MX (Mail eXchange) record will redirect email sent to any user's machine to a designated mailhost.
It tells the MDA where to route email.
MX records point to an SMTP delivery service that receives email for the given domain.
It points to hosts that handle only smtp requests (which arrive at 25 tcp port by default).

Or to say, why the result is not as below?

Code:

dig 163.com -t mx
;; ANSWER SECTION:
163.com.        6212    IN  MX  10  123.125.50.133
163.com.        6212    IN  MX  10  123.125.50.138

Because you are making assumptions about mail handling.

The published MX servers for the domain you are looking at are 163mx01.mxmail.netease.com, 163mx03.mxmail.netease.com, 163mx00.mxmail.netease.com, 163mx02.mxmail.netease.com

Just because smtp.163.com returns IP records does NOT mean that those servers are publicly accessible or handle inbound mail for that domain. Those may be smtp servers for customers of that ISP to use for outbound mail, it has ZERO relationship to how inbound mail for that domain is handled.

luofeiyu · 09-28-2017, 06:14 PM

Conclusion from many reading and TenTenths' answer.

The role of MX records is: to point to an SMTP delivery service that receives email for the given domain.
The role of smtp.163.com is : to send email to others by its users.

For the same mail server ,the two server's ip can be the same one ,or not.

right or not?

TenTenths · 09-29-2017, 03:31 AM

Quote:

Originally Posted by luofeiyu

The role of MX records is: to point to an SMTP delivery service that receives email for the given domain.

Yes
--

Quote:

Originally Posted by luofeiyu

The role of smtp.163.com is : to send email to others by its users.

Probably
--

Quote:

Originally Posted by luofeiyu

For the same mail server ,the two server's ip can be the same one ,or not.

These are not going to be single mail servers in this instance. Any server can have more than one IP address.