How AutoArchive works in Outlook
Outlook mailboxes grow as users create and receive items. To keep mailboxes manageable, users need another place to store - or archive - older items that are important but not frequently used. It is typically most convenient to automatically move these older items to the archive folder and to discard items whose content has expired and is no longer valid. AutoArchive manages this process automatically for users.
Scheduling automatic archiving
AutoArchive is on by default and runs automatically at scheduled intervals, removing older and expired items from folders. Older items are those that reach the archiving age a user specifies (the default archiving age varies by the type of Outlook item). Expired items are mail and meeting items whose content is no longer valid after a certain date, such as a mail item set to expire two months ago that still appears in a user's Inbox.
Users can specify an expiration date on items in Outlook at the time they create or send the item or at a later date. When the item expires, it is unavailable and shows in a folder list with a strike-out mark through it.
Outlook takes in consideration the Modified date and if you notice that there are messages that are not archived, this will be the very first thing to check.
Archive folder location
When AutoArchive runs, it can delete items or move items to an archive folder, depending on the settings you specify.
The archive file is an Outlook data file (PST file) that appears as Archive Folders in the Outlook folder list. The first time AutoArchive runs, Outlook creates the archive file automatically in the following location:
%UserProfile%\Local Settings\Application Data\Microsoft\Outlook\Archive.pst
How retention settings work in Outlook
In addition to the AutoArchive settings, you can also enable retention policy settings for items in user mailboxes. Retention policy settings can help users to follow retention policy guidelines that your company establishes for document retention.
Because retention policies settings are part of Outlook's AutoArchive functionality, retention settings only run when AutoArchive is run. Running an archive manually does not trigger retention settings enforcement.
Retention Group Policy settings in Outlook can be configured to follow company policies, to encourage users to retain documents and items for only a fixed period of time. Retention settings implementation requires AutoArchive to be enabled, but retention settings take precedence over AutoArchive settings.
The following registry keys let's you control the retention policies. These are located under:
Note: 1x.0 (depending on your Outlook version i.e. 12.0 for Outlook 2007)
Note : If RetentionOn is turned off (disabled) or missing from the registry, a message in the AutoArchive dialog box states the following:
The network administrator has not set retention policies for this mailbox.
If retention policies are enabled you will be able to see in Auto Archive dialog box the following message. Also this message will be displayed in your folders:
Note: Retention policies are applying also on PST folders. Because retention policies settings are part of Outlook's AutoArchive functionality, Retention Settings only run when AutoArchive is run. Running an archive manually does not trigger Retention Settings enforcement.
Can a user create a search folder that shows messages that will be deleted due to retention in the next n days?
I'm looking for the same thing that Bob C above is looking for: a search folder that shows messages that are about to expire.