Re: [exim] Exim as a backup MX server

On 07/04/2020 21:33, Andrew C Aitchison via Exim-users wrote:
>> Getting that knowlege depends on your existing setup.
>> Possibly it's a case of pointing Exim at your AD server,
>> and hoping it really does talk LDAP sanely.
>
> Exim does recipient callouts and cutthrough delivery.
> Are either of these useful for an MX backup ?

Yes, but limited in that they can only discover the
(non)existence of accounts when the primary is up.

You'd have to decide on policy and implementation for
when it isn't - eg. a getting-stale (but local) user
database. Refusing connections wholesale would defeat
the object of having the secondary.

Using them does have the advantage that per-user filtering
(including, for cutthrough, body-scanning) is localised
in one place.


Of course, requiring that your ldap server(s) stay up
is an issue in itself.
--
Cheers,
Jeremy