[Exim] Frozen message management

Hi all,

I have a mailserver with a full mailqueue - it's turned out there are
frozen messages in this queue from the last four months.

I would like the system to deal with undeliverable messages on their own
- in other words I would like failed messages to bounce, and double
bounces to be deleted so as to prevent the mailqueue clogging up.

How do I do this?

Regards,
Graham
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