Outlook’s auto-archive feature moves old emails out of your main mailbox automatically, either to a local archive file (PST) or to your Online Archive in Microsoft 365. Setting it up reduces mailbox size without manual cleanup and keeps older items accessible when you need them.
Two Types of Archiving in Outlook
It is worth understanding the difference before setting up:
- Auto-archive to PST (local file): moves items to a .pst file stored on your computer. Items are removed from the Exchange server. They are accessible in Outlook on that machine but not via Outlook Web Access or other devices unless you copy the PST file.
- Online Archive (Microsoft 365): if your IT team has enabled the Online Archive, it appears as a second mailbox in Outlook. Items moved there stay on the Microsoft 365 servers and are accessible from any device. This is generally the better option for business use.
Setting Up Auto-Archive to PST
- Go to File → Options → Advanced
- Under AutoArchive, click AutoArchive Settings
- Tick Run AutoArchive every X days (14 or 30 days is common)
- Configure the options:
- Delete expired items (email folders only): permanently deletes items past their expiry date — leave unticked unless you want items to be deleted rather than archived
- Archive or delete old items: tick this to enable moving items to the archive file
- Clean out items older than: set the age threshold, e.g. 6 months or 1 year
- Move old items to: set the PST file location or keep the default
- Click OK
Setting Archive Rules Per Folder
You can set different archive ages for individual folders — useful if you want Inbox items archived after 6 months but want to keep Sent Items for longer, or never archive Contacts and Calendar.
- Right-click any folder in Outlook and select Properties
- Click the AutoArchive tab
- Choose one of:
- Do not archive items in this folder — exempts this folder entirely
- Archive items in this folder using the default settings — inherits global AutoArchive settings
- Archive this folder using these settings — lets you set a custom age for this folder
Using the Online Archive (Microsoft 365)
If your organisation has enabled the Online Archive, you will see it in Outlook’s folder panel as In-Place Archive — [your name] or Online Archive.
To move items there manually: drag and drop folders or individual messages into the Online Archive. To archive automatically, ask your IT administrator to configure a Retention Policy in Microsoft 365 that moves items older than a set age to the archive automatically — this is the recommended enterprise approach.
Archiving Immediately (Manual Archive)
To archive items now without waiting for the AutoArchive schedule:
- Go to File → Info → Tools → Clean up old items (in some versions: File → Archive)
- Choose whether to archive all folders using default settings or a specific folder
- Set the cutoff date — items older than this date will be moved
- Click OK
Accessing Archived Items
If you archived to a PST file, the archive appears in Outlook’s folder panel under Archives or as a separate data file. Search works across both your main mailbox and the archive simultaneously. To search only the archive, click into the archive folder structure first before searching.
Exporting vs Archiving
Archiving in Outlook automatically moves items on a schedule. Exporting to PST is a manual one-time process that copies (not moves) items to a PST file — the original items stay in your mailbox. Use File → Open & Export → Import/Export → Export to a file to create a PST backup without removing items from your mailbox.
