Recommended Limits for Exchange on Several Platforms

I am interested in finding the following information

1.) Maximum recommended number of items per folder
2.) Maximum recommended number of nested folders
3.) Maximum recommended number of overall mailbox size
4.) Maximum recommended item/attachment size (for both incoming and outgoing emails)

I am interested in this info both as it applies to Exchange 2003 and 2007, as well as the folliwing apps:

Outlook 2003
Outlook 2007
Entourage 2004
Entourage 2008

I have had issues with large hosted exchange mailboxes interfacing with Entourage (2004). I have also had users to have more than 2,000 items in any folder (especially inbox, deleted, etc) slowing down or working poorly as a result.

Any help would be appreciated.

Thanks.