i configure to mx ,one as master ,other as backup
dns configure look like:
first mx:
---------------------
121.90.8.77 ----> test111.domain
pop------->121.90.8.77
smtp------->121.90.8.77
@ IN MX 10 test111.domain
--------------------
second mx
webmail.test111.domain IN A 121.90.8.78
test111.domain IN MX 5 webmail.test111.domain

mx point to different mail server.
my question:
mx level 5 server should get the mail first.why not?

It is hard to tell without any information about how did you find this out. What test methods you used to test it.
The possible answer to your question is: that there has to be some trouble with the master server and this is why the backup is used.

the master mail server work fine,but the webmail support chinese not well.so i configure other mail system(include webmail)to instead it ,
so i have to configure two MX ,just keep user no feeling when i swtich them.

test method:
send mail with other mail system online to the user in myown mail system,
mx level 5 server should get the mail first,i think ,but it is not....

Any one ayn seguesstion will help me out...thx

Try looking in the logs of the system that you sent the mail from and on the server. Check both the DNS and the mail logging (and enable logging if it isn't). It is possible that it tried to get the mail to the desired server, but couldn't for some reason.

Also try to query your DNS and set the record type to MX (typically 'set type = mx') and run the query for the root domain (test111.domain) and see what is returned. Repeat the process using webmail.test111.domain. Similarly run a regular DNS query against webmail.test111.domain to see if it resolves the proper address.

Lastly, do you know for certain that the webmail.test111.domain mail server is working correctly? In other words are clients able to connect to it without error?

One other option to consider would be to have your primary mail server forward to the secondary one for certain users.

i got nothing for maillog or dns log.
so i think ,mx as backup ,under this condition:
when master mail server was down

Hi xiutuo,

Actually, MX entries at DNS zone records/database doesn't provide failover/backup for ur mail receiving. DNS only resolves/try to resolve the all MX entries even if they are down in round-robin manner. So better do the followings:

1.In DNS make the priority difference high one MX for 0 and other around 90 server due to which 0 is high priority and get the server normally previously than 90 but it doesn't happen always in my experience also. Go for second step.
2.There is a free package called "balance" which is very best for load balancing as well as for fail over.
http://packages.sw.be/balance/

I think it might help u.

thank u
any document about blance(give me a url)?
i googled,but lots of things nothing to do with it..