How to Delete Outlook Mail Cache
If Outlook starts freezing or not responding, it might be because it's trying to handle too much old email cached on your computer. Here's how you can clean it up:
Please Note: deleting the local mail cache will also delete any unsent mail in the Outbox or Draft folders, if these have not been synced to the server.
- Close Outlook before you start,
- Go to your computer's stored email folder. You can do this by pressing the "Windows" key + "R" on your keyboard to open the Windows Run menu.
- Then type C:\Users\%USERNAME%\AppData\Local\Microsoft\Outlook into the Windows Run menu and click "OK"
- Once you're in the "Outlook" folder you'll want to delete all the files within it. Make sure all other Microsoft 365 programs are closed too, or some files might not delete. To do this, first highlight everything inside the "Outlook" folder by pressing "CTRL" + "A", then press the "Delete" key.
- Restart Outlook. All previously cached mailboxes will need to be downloaded again. This may take quite some time for shared mail accounts. Outlook may freeze up and become non-responsive at times while the mailboxes are downloaded. Trying to open any mailbox before enough of it has downloaded will trigger an error message to the affect of "The set of folders cannot be opened [...]". Will need to wait until the Outlook status bar at the bottom of the window reports the mailbox is nearly synced again.
What is The Outlook Cache
Outlook caches email (1-year by default policy) on the computer's local hard drive for each email account added to an Outlook Mail Profile. This reduces network overhead, as the mail client doesn't need to communicate with the mail server for each action when working with email.
Some Causes of Bad Email Cache
- Too many accounts added to mail profile as "Open Additional Mailbox" rather than as separate accounts
- Cache file(s) bloated - Maximum Size of 50GB for individual .pst files
- Large number of mailbox or calendar folders
- Mail profile with a large number of added accounts