[CentOS] multiple MX records

Kai Schaetzl maillists at conactive.com
Thu Nov 10 14:31:45 UTC 2005

Tom wrote on Fri, 11 Nov 2005 01:19:57 +1300:

> I have 2 servers, 1 is DNS master and the other slave for a domain, if I 
> was to add a second MX record using the master servers IP for the domain 
> thats hosted on the slave would mail be held on the masters mail queue 
> if the slave was down?

Forget about the dns master/slave, mentioning that just complicates it, 
mail queueing is independant of dns setup. If you add a second MX of lower 
priority mail will be sent to it if the MX of higher priority is not 
available. But you have to configure the backup MX accordingly so that it 
actually queues the mail and doesn't reject or try to deliver it locally. 
With sendmail you have to allow relaying for that domain but don't add it 
to the Local Domains list! Other mailers may need different actions.
Be aware that lots of spam will be attracted by the backup MX!


Kai Schätzl, Berlin, Germany
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