Re: [exim] configuring backup mx

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Author: Tony Finch
Date:  
To: Asbjorn Aarrestad
CC: exim-users
Subject: Re: [exim] configuring backup mx
On Wed, 5 Oct 2005, Asbjorn Aarrestad wrote:
>
> What happens when my server tries to deliver the mail to the primary mx
> and fails? Will it try to deliver the mail to the secondary (itself), or
> will it just fail the delivery and wait for the next retry time?


No and yes. Section 17 of the spec says:

MX records of equal priority are sorted by Exim into a random order. Exim then
looks for address records for the host names obtained from MX or SRV records.
When a host has more than one IP address, they are sorted into a random order,
except that IPv6 addresses are always sorted before IPv4 addresses. If all the
IP addresses found are discarded by a setting of the "ignore_target_hosts"
generic option, the router declines.

Unless they have the highest priority (lowest MX value), MX records that point
to the local host, or to any host name that matches "hosts_treat_as_local",
are discarded, together with any other MX records of equal or lower priority.

If the host pointed to by the highest priority MX record, or looked up as an
address record, is the local host, or matches "hosts_treat_as_local", what
happens is controlled by the generic "self" option.

Tony.
--
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