Managing emails in Zimbra 7.2

[phr1]

Hello,
I have a couple of questions regarding email management in Zimbra 7.2:
- how can you tell how full the In- and Outboxes are?
- how do you prune emails in the Outbox? Do you just scroll down to the oldest emails (day 2010) and delete your way up to the most recent ones?
- when do you archive emails?
- should you archive both Inbox and Outbox emails?
Many thanks.
Cheers,
phr1