Archive items manually

Your Outlook mailbox is only so big, and it’s a good bet that you won’t stop getting an email anytime soon. To keep it from filling up, you can move old items you want to keep to an archive, a separate Outlook Data File (.pst) that you can open from Outlook any time you need it.

Note:  The Archive command and feature doesn’t appear for any account in your Outlook profile if you include an Exchange Server account and your organization uses Microsoft Exchange Server Online Archive. Your network administrator can also disable this feature.