beemerboy

hi folks,
just built an exchange2003 server for a client, and asked the isp (current mail host) to change the mx record to xxx.xxx.xxx.xxx

now he has turned around and asked me for the following information:

MX 1 / Prio
MX 2 / Prio
Further backups My mail exchangerBackup mail exchanger
MX 3 / Prio
MX 4 / Prio

WTF??

any help mucho appreciated...

BB

ChrisB

Each MX record has a numerical value for the priority.

The lower the value, the higher priority. So if you have two MX records defined for your domain, one with a Pri of 5, the other with Pri 10, remote mail servers sending to you would try the 5 server first. Then they would fall back to the 10 if the 5 didn't respond.

So in your case MX 1 (with say a Pri of 5) would be your new Exchange server.

MX 2 (Pri 10) would be another server somewhere which accepts mail for the domain. If your Exchange goes down, you can then retrieve the mail from the second server.

beemerboy

ah, that makes sense...

many thanks Chris.

The ISP guy was getting all geeky on me..

BB

ChrisB

No problemo.

Just to add, you can have MX records with the same priority value if you want to split inbound traffic between servers. Big ISP or mail services use this (eg AOL).

You don't have to have a backup MX set but it's good practise to have some sort of fall back. A remote mail server should retry sending a message several times over 24 or 48 hours (depends on it's config) and then bounce it back to the sender.