Symptoms
Being unable to recieve mail and seeing the following error in the exim_rejectlog:
2021-08-27 21:01:20 H=mail-oln040092255043.outbound.protection.outlook.com [40.92.255.44]:20516 temporarily rejected connection in "connect" ACL: ratelimit database not available
Description
This issue is caused by a missing exim database file, the ratelimit database file:
/var/spool/exim/db/ratelimit
Workaround
Moving the entire Exim database directory then restarting Exim will cause Exim to recreate the database directory along with the ratelimit database:
mv -v /var/spool/exim/db{,.bak$(date +%s)}
/scripts/restartsrv_exim