[exim] Silly situation - reprocess mail in queue

Hello everyone,

I have a 'backup' host configuration which accepts the mail when the
server with higher MX is down:

manual_route:
         transport = remote_smtp
         driver = manualroute
         domains =  +relay_to_domains
         route_list = btw2.pl 77.253.234.172 ; btw2.eu 77.253.234.172
         unseen

Since the router is unseen, Exim also processes mail normally and stores
it locally to enable users read mail on the backup host when the main
host is down.

Well, a silly thing happened: another administrator cleared the setuid
bit on exim binary and exim was unable to save the incoming mail locally.

The mail was obviously not lost since it's in the queue and will be
delivered when the main host goes online.

But I would like to make Exim save that mail again on backup host, that
is, to reprocess each mail in the queue as if it were just incoming over
SMTP, so it could save the local copy.

Is there a way to do this in Exim? I don't want to muck about manual
delivering spool files to user maildir folders.

Regards,
mk