1. Go to File > Info.

2. Click Cleanup Tools next to Mailbox Cleanup and select Archive…

outlook mailbox cleanup

3. Choose the folder you want to archive. Outlook will save that folder and all the subfolders beneath it. If you choose "Outlook" (the highest level folder), all of the items in Outlook will be moved to a new data file.

outlook archive options

4. Select your archive options, such as item date. You can change how old emails (or other items) have to be before they get archived and also choose or create a different .pst file.

5. Click OK and Outlook will start archiving your mail and other items, depending on the folder you selected.