Note: With the 100GB quotas on Office 365, most users will not need AutoArchiving. If you do you use it, keep in mind that your .pst file is not automatically backed up.
To help keep mailboxes manageable, you need another place to store, "archive", older items that you need to reference but are not used all the time. Outlook has a built-in feature called AutoArchive that stores Outlook items (messages, appointments, tasks, notes, etc.) in a different location. Items are moved to an archive file. AutoArchive copies items to the archive file (default - archive.pst) and then removes them from the current folder. It allows you to set up a schedule and archive multiple folders at the same time at set intervals. You can also individually select folders for archiving.
The first time AutoArchive runs, Outlook creates the archive file automatically in the following location:
C:\Users\username\Documents\Outlook Files\archive.pst
We recommend you do not change the name or location of the archive file because it could be hard to locate if you forget the name/location.
The default for AutoArchive is to prompt you every 14 days to archive your items older than 6 months and any expired items. Expired items are messages and meeting items that are not valid after a certain date (e.g., message set to expire 1 month ago that is still in your Inbox).
The default aging periods for folders are:
Inbox, Calendar, Tasks, Notes, Journal, Drafts: 6 months
Sent Items, Deleted Items: 2 months
Outbox: 3 months
Outlook determines the age of an item based on the item type:
Email message - The sent or received date or the last modification date/time, whichever is later.
Calendar item - The appointment, event, or meeting date or the last modification date/time, whichever is later. Recurring items are not Auto Archived.
Task - The completion date or the last modification date/time. Tasks that are not marked complete are not Auto Archived. Tasks assigned to others are archived only if marked complete.
Note - The last modification date/time.
Journal entry - The date the journal entry was created or the last modification date/time.
Contacts - Not archived.