Ollie Cook <ollie@???> wrote:
>
>If the mail is queued on a secondary MX under your administrative control
>it's much easier to control the sending on of the mail to the primary hosts
>when they come back online.
>
>One other crucial point about having your own secondary MXes is that you will
>probably elect to hold mail for your site for longer than a remote site may,
>which would be a factor if your primary mailservers were down for a long time.
>
>All in all, I think you do benefit quite a lot from running your own secondary
>MXes rather than relying on remote sites to hold onto the mail.
This argument assumes that your primary MX is sufficiently unreliable
that you need some kind of local backup in addition to SMTP's built-in
resilience. I would focus on reliability before worrying about backup MXs.
The biggest problems with backup MXs are that they must implement the
same security policy as the primary MXs, and they must work when things
are in the shit despite the fact that they can be broken most of the time
without anyone noticing. The first requirement has serious implications
for resource-heavy SMTP-time checks, and even if you only have lightweight
checks you must still have a lot of control over the machine in order
to verify addresses etc. The second requirement puts heavy demands on
your update and testing procedures -- I see little point in a machine
that requires sysadmin time without doing much useful work.
Tony.
--
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