DNS MX Record must be placed before a record, otherwise, the domain name that matches the mail suffix does not point to the mail server, and the mailbox will not receive the mail.
For example, as follows:
My Mail suffix is Wa-wa.com.cn, and the DNS MX is recorded as mail.wa-wa.com.cn, and the mail server IP is 210.75.18.37, Wa-wa.com points to 211.96.97.30, mail.wa -wa.com.cn points 210.75.18.37
If my DNS configuration is as follows, then my mail server
Wa-wa.com.cn is the suffix of mailboxes
Can't receive email
Wa-wa.com.cn. 3600 in ns ns1.dns.com.cn.
Wa-wa.com.cn. 3600 in ns ns2.dns.com.cn.
Wa-wa.com.cn. 3600 IN A 211.96.97.30 # Wa-wa.com.cn. A before the MX record, and wa-wa.com.cn. A record does not point to the IP address of the mail switch, Therefore, the mailbox for the mail server Wa-wa.com can not receive the email wa-wa.com.cn. 3600 in mx mail.wa-wa.com.cn.
Mail.wa-wa.com.cn 3600 in A 210.75.18.37
Www.wa-wa.com.cn 3600 in A 211.96.97.30
Cp.wa-wa.com.cn 3600 in cname mydns.dns.com.cn.
Pop3.wa-wa.com.cn 3600 in A 210.75.18.37
SMTP.WA-WA.COM.CN 3600 in A 210.75.18.37
DNS A records and MX record resolutions are replaced below.
The modified resolution order is as follows:
Wa-wa.com.cn. 3600 in ns ns1.dns.com.cn.
Wa-wa.com.cn. 3600 in ns ns2.dns.com.cn.
Wa-wa.com.cn. 3600 in mx mail.wa-wa.com.cn. # MX is recorded before Wa-wa.com.cn. A, even though wa-wa.com.cn. A records Point to the IP address of the email switch, but the mailbox for the mail server Wa-wa.com is a complicated mailbox or the mailbox. 3600 in A 211.96.97.30
Mail.wa-wa.com.cn 3600 in A 210.75.18.37
Www.wa-wa.com.cn 3600 in A 211.96.97.30
Cp.wa-wa.com.cn 3600 in cname mydns.dns.com.cn.
Pop3.wa-wa.com.cn 3600 in A 210.75.18.37
SMTP.WA-WA.COM.CN 3600 in A 210.75.18.37
Mail Send Principle: Mail Server Send Mail First Looking for DNS MX Records, if the Find MX record fails, then use A record transceiver, and I have written in this case if the MX record before MX record, at the same time There is no IP210.75.18.37 that points to the email switch, the system is possible to record the send and receive mail with Wa-wa.com.cn A, so I can't accept the mailbox of Wa-wa.com.cn, this should be DNS MX record must be placed before a record
reference:
Http://chinalinuxpub.com/vbbforum/showthread.php?s=&postid=247382#post247382
