Would it be possible to implement a queue system which utilises a short and
long queue system?
(Possible method)
The e-mails in the queue which are waiting for a retry are moved to a
secondary queue which is only checked every N minutes (maybe 15-60 minutes)
until their expiry time.
This dramatically changes the delivery times on sites with as much traffic
as ours (I assume because the queue runners don't check if they need to
deliver the older e-mails)
