How to clear Outlook cache on Mac
Microsoft offers a way to clear Outlook cache on Mac as a fix for sync problems, such as missing or wrong items, rather than as a way to free space. Outlook deletes its local copy and downloads your mail from the server again, and anything never synced with the server is lost. New Outlook and legacy Outlook do it differently, and this guide covers both.
- Open MacWashing and choose System Junk in the sidebar.
- Click Start Scan.
- Look through what it found and click Clean. Anything debatable stays unchecked.
Free trial · macOS 14 or later
New or legacy Outlook?
Outlook for Mac comes in two versions. New Outlook is the current one. Legacy Outlook has a Legacy Outlook switch you turn off to move to new Outlook. Starting October 2026, legacy Outlook stops working with Exchange Online (Microsoft 365) mailboxes. It keeps working with on-premises Exchange servers until October 9, 2029.
How to clear Outlook cache on Mac (new Outlook)
Resetting the account deletes everything in it that isn’t synced with the server, then downloads the account again.
- Make sure your Mac is connected to the internet and to the mail server.
- Choose Tools › Accounts.
- Select the account you want to reset.
- At the bottom, click Manage and choose Reset Account.
Empty the cache of a folder (legacy Outlook)
Legacy Outlook clears the cache one folder at a time, for Exchange accounts. Emptying it deletes whatever in the folder isn’t synced with the Exchange server, including your contacts’ mail certificates, and replaces the contents with the latest items from the server.
- Make sure your Mac is connected to the Exchange server.
- In the folder list, Control-click the Exchange folder and choose Properties.
- On the General tab, click Empty Cache.
- Wait while Outlook downloads the folder’s items from the server again.
Before you reset: what can be lost
- Anything that exists only on this Mac and not on the server. Microsoft advises backing up your Outlook data first.
- In legacy Outlook, your contacts’ mail certificates in that folder.
Don’t delete Outlook’s folders in Library by hand. ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles holds your Outlook profile with its local mail, and Outlook’s own reset is the safe way to rebuild it.
With MacWashing, it’s one click
System Junk in MacWashing finds the caches of your apps, shows how much each takes and clears them in one go. Anything debatable stays unchecked until you decide. For Outlook sync problems, use Outlook’s own reset above.
Free trial · macOS 14 or later
Questions and answers
Will MacWashing delete my own files when it cleans?
No. It removes only what it can match to a known app or a known kind of junk, in places apps leave files; macOS and Apple’s files are never touched. Anything debatable is marked and stays unchecked until you decide.
What about apps that are open?
If an open app holds files being cleaned, MacWashing waits for it to quit or quits it at your request, and opens it again afterwards.
Is it free?
Yes, within the free trial: System Junk and the Uninstaller free up to 25 GB in total, with no account or card needed.
Will clearing Outlook cache on Mac delete my emails?
Mail that is stored on the server downloads again. Only items that were never synced with the server are lost, which is why Microsoft suggests a backup first.
Which Outlook has the Empty Cache button?
Legacy Outlook, in the properties of an Exchange folder. New Outlook has no per-folder button: it resets the whole account from Tools › Accounts.
Does clearing the Outlook cache free up space?
Only for a while. Outlook downloads your mail again after the reset, so the space fills up as the account syncs.