[Exim] domain in relay_domains, exim being best mx, now what…

hi,

i have a mail hub. a number of domains are defined as relay_domains to
exim, but in dns, the lowest-priority mx is the mail hub itself (then
a router routes the messages to their final destination. this is a
working setup).

the basic question is, what happens now ?

to be more specific, one of the nodes connected to the hub is down for
some time now, and mails are being queued on the hub (as expected).
however, i see no retry data for this domain (or any domain, to be
precise). now that i'm writing, i remember a number of cases, when i
saw a couple of mails (to other domains, same mail hub) sitting on the
queue for a while, and a queue run delivered them fine - there might
have been a temprary failure, but those messages had never been
retried. i didn't pay much attention, honestly, i thought these were
some hiccups.

can this be the case ? what happens to the momentarily-undeliverable
messages ? how are the retry rules apply (in general in that
situation) ?

i feel kindof confused.

thanks,

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