It would be VERY useful to have a quarantine queue PER USER (or at least PER DOMAIN)...

Let me explain...

INCOMING:

Having a global incoming quarantine queue is of little use, because super admins DON'T know what various domains/users are supposed to receive and DON'T have the time to check the incoming queues of THOUSANDS of different users...

Users themselves should check their OWN quarantine queues, so they can better determine if anything is blocked and flag the rest as SPAM.

...at best, it could be PER DOMAIN, with domain admins assigned to check it (not optimal, but better than nothing...)

OUTGOING:

In this case, it would be nice to enable a quarantine queue at least PER DOMAIN, so that domain admins could see the outgoing emails that have been blocked.

I think having it per user is less useful in this case.