[Exim] mail queuing

Hi,

is it possible to queue mails when a mailserver goes down?

Exim is a mailhub here.
Behind exim there are two mailservers for two domains.

When the mailserver for domain b goes down - is it possible that
exim suppresses delivering for a few days or puts the mails
into files as long as this mailserver is not reachable??

We don't want to do this with the retry configuration.
Any hints or tips?

Michael