Hello.

I've got two MX records for my domain, one with priority 20, the other with 30, like so if we dig:

mydomain.com. 84828 IN MX 20 s1.mydomain.com.
mydomain.com. 84828 IN MX 30 s2.mydomain.com.

now, what happens is that eventhough s1.mydomain.com hasn't gone down since we started testing, some few emails are going through to s2.mydomain.com.

Admittedly, only a fraction of emails are doing this, but some important emails are going through to s2.mydomain.com. It has a only catchall account since we plan to use it for emergencies only - people don't check mail on s2. Any ideas as to why this is happening - any suggestions? Do we have to check both mailservers for mail then?

thanks,
branden_burger

Hi,

when you set 2 MX records on your DNS config, both will be used.
The weightig is only here so that mailservers do some loadsharing between them.
If you want only backup, then the only real way to do it is to configure both mailservers as part of a cluster.
There are certainly some workaround, like using a script on the backup to monitor the main mailserver and take its place if its down, but i really think the cluster solution is the only long-term.

You have 2 machines trying to be the mail server. I only have experience with QMail (not sure what you're running), but you'd set up s2.mydomain.com to be a caching-only mail server. It would accept emails for mydomain.com, but would hold them until s1.mydomain.com is ready to accept them (in the event it's busy or offline). If you're looking for redundancy, you may look at a program called heartbeat (Sourceforge or Freshmeat, don't remember which) that would have s2 as a backup of s1 (replicating the files via rsync constantly), until s1 goes down. Then heartbeat would make s2 look like it's s1, assuming it's IP address and all. Get's a little more complicated if you're using MySQL for any storing of email or addresses.

hmm, i thought as much. clustering/load balancing is a solution...could experiment with rsync and heartbeat though.

Thanks!!