Fix search issues by rebuilding your Instant Search catalog - Microsoft …
Symptoms of an incomplete index include the following: Partial or no search results are returned. Items that you expect to appear based on your search criteria aren't displayed. You can rebuild the search catalog, which restarts the indexing of your data files.
Information about Store my Outlook settings in the cloud
Store my Outlook settings in the cloud is enabled by default and available for Microsoft 365 accounts with cloud mailboxes using the latest Monthly Enterprise Channel, Current Channel, or Semi-Annual Enterprise Channel (version 2108). It is also available for Outlook.com users.
Open and find items in an Outlook Data File (.pst)
Describes how to investigate items in an Outlook Data File (.pst) and troubleshoot search issues.
Introduction to Outlook Data Files (.pst and .ost)
Learn How to remove an Outlook .pst data file from OneDrive. Note: In earlier versions of Outlook, IMAP accounts also used an Outlook Data File (.pst). In Outlook 2016 and Outlook for Microsoft 365, IMAP accounts use Offline Outlook Data Files (.ost).
Repair Outlook Data Files (.pst and .ost) - Microsoft Support
You can use the Inbox Repair tool (SCANPST.EXE) to diagnose and repair errors in your Outlook data file. The Inbox Repair tool checks the Outlook data files on your computer to see if they're in good shape. You might want to use the Inbox Repair tool in the following situations:
Create an Outlook Data File (.pst) to save your information
When you add an email account to Outlook, a local copy of your information is stored on your computer. This feature allows you to access your previously downloaded or synchronized email messages, calendar information, contacts, and tasks without an internet connection.
Manage your Microsoft 365 subscription or Office product
You can manage all of your Microsoft subscriptions in your Microsoft account dashboard. Select each subscription to change when and how you pay, or to see order history & receipts. Choose your account type.
Find and transfer Outlook data files from one computer to another
Outlook stores backup files containing email, calendars, contacts, tasks, and notes on your computer. Learn how to find them.
Export emails, contacts, and calendar items to Outlook using a .pst ...
After you create the .pst file, copy it to a safe location: a USB flash drive, another hard drive, or cloud storage such as OneDrive or Dropbox. There's no automated way to periodically backup everything (old and new).
Import and export Outlook email, contacts, and calendar
Find the information you need to import to or exporting from Outlook, whether you're using Office 365, Outlook 2016, or a Mac.
Recover and restore deleted items in Outlook - Microsoft Support
When you accidentally delete Outlook items, such as email messages, calendar appointments, contacts, or tasks, you can often recover them if they are in your Deleted Items or Junk Email folders. In some cases, you can even recover items after the Deleted Items folder is emptied.