Microsoft Outlook stores files you've used so that it can easily access them again. These files are known as cached files and can be safely deleted. Clear the Outlook cache if old data remains after you delete it, something that may happen when you remove and reinstall Outlook add-ins. Another reason to delete cached files is if autocomplete data or other information displays after you delete contacts or reinstall Outlook.
Instructions in this article apply to Outlook 2019, 2016, 2013, 2010, 2007; and Outlook for Office 365.
Removing the cache in Outlook doesn't delete emails, contacts, or other useful information.
Save any work and close Outlook.
Press Windows key+R.
In the Run dialog box, enter %localappdata%\Microsoft\Outlook and press Enter.
Double-click the RoamCache folder to view the cache files.
Back up the cache files so that you can restore the files if something goes wrong.
To delete the cache files, press and hold the Shift key while selecting all of the files. Then press the Delete key, or right-click the highlighted files and select Delete.
Outlook automatically makes new cache files when you open Outlook.
If you only want to clear the auto-complete cache, either turn off auto-complete so the cached data doesn't display or delete the auto-complete cache completely.
Go to the File tab and choose Options.
In the Outlook Options dialog box, select the Mail tab.
In the Send messages section, clear the Use Auto-Complete List to suggest names when typing in the To, Cc, and Bcc lines.
If you want to clear the auto-complete cache, select Empty Auto-Complete List. In the confirmation dialog box, select Yes.
Clear the cache to remove the auto-complete history without disabling the auto-complete feature in Outlook.
In the Outlook Options dialog box, select OK.
The Auto Complete List is a feature which displays suggestions for names and email addresses as you begin to type them. The first time you enter a person’s name when addressing an email, Outlook searches for that person’s address from the contacts list. After the first email is sent to that person, their name will be saved so it can be found quickly the next time you email them. Sometimes you will have an old email address in the Auto-Complete that you will want to delete.