[Dovecot] Expunge deleted messages older than X days for all users ?

[Bar Ziony]

Hi,

I'm currently migrating to Dovecot-based IMAP server for a ~200 users 
environment. Clients are Outlook 2003/2007, Thunderbird 3.x and various 
mobile clients.

1) What I want to accomplish is to allow the users to delete a message 
(then the message is moved to "Trash"), then when they empty/delete that 
message from Trash, it will be kept somewhere on the server for X days, 
and the user could recover that message in some way.

Is that at all possible with Dovecot?

2) Also, how can I automatically expunge the emails that the user 
deleted from their deleted items folder ? What if users don't EXPUNGE by 
themselves ? What do you do in that case?

Thanks,
Bar.