Microsoft Exchange's Deleted Items Retention feature is turned on by default and one day it'll save you contemplating a whole mailbox restore.
I've used Outlook and Exchange for many years but it was only recently that I discovered what Deleted Items Retention is all about. First of all, it's important to understand that this is a feature of Exchange, not Outlook (although you use it via Outlook). It also doesn't apply to mail you keep in a local .PST file - only to the Exchange mailbox.
One of our users had been asked to clean up his mailbox as he was approaching his quota. At one point he deleted some messages, not realizing that they still took up space in the Deleted Items folder. Later in the process, he was advised to empty Deleted Items and with some other housekeeping his mailbox returned to an acceptable size.
A day later he came to us claiming he couldn't find some important emails. We asked where he expected to find them. "In the Deleted folder," came the reply. Laying aside the question of why he deleted them in the first place, we had to gently break the bad news that because he'd emptied Deleted Items they were gone. One unhappy user.
I knew our backup software could restore the whole Exchange database and was fairly confident it could even do individual mailboxes, but either way this wasn't an appealing prospect, especially as going back to the last backup before the deletion would inevitably mean the loss of other (and probably more important) emails! At this point I remembered seeing something about deleted items retention in Exchange and decided that now would be a good time to check it out.
Having consulted the Help in Exchange I simply went to the user's Deleted Items folder in Outlook and selected Tools / Recover Deleted Items.... The resulting dialogue showed me the messages recently purged from Deleted Items, enabling me to select & recover the messages he'd really intended to keep. Simple.
This also works in folders other than Deleted Items where you "permanently" deleted a message by using Shift-Delete.
(Although I got my instructions from Exchange, the Help in Outlook explains this well (for once). Just search on "recover deleted items".)
Exchange configurationFortunately for us, Deleted Items Retention is configured by default, at least in Exchange 2007. The database-wide defaults are set via Server Configuration / Mailbox; in the Database Management tab, right-click your mailbox database and click the Limits tab to view or change the settings (Figure A). As the Help points out, increasing these settings will increase the size of your mailbox database. Figure A
Notice too that Exchange will also retain deleted mailboxes; obviously you can't recover an entire mailbox from Outlook - that's done in Exchange via Recipient Configuration / Disconnected Mailbox.You can also configure Deleted Items Retention on a per-mailbox basis, in the same way that you can set individual mailbox quotas (Figure B). Simply uncheck Use mailbox database defaults and enter your desired number of days. Figure B
Deleted Items Retention is a helpful feature of Microsoft Exchange that saved us resorting to backup tapes when we needed to recover emails inadvertently purged from the Deleted Items folder in Outlook.