To clear the Outlook cache in classic Outlook on Windows 10, close Outlook, press Windows logo key + R, open %localappdata%\Microsoft\Outlook\RoamCache, and delete what’s inside. For the new Outlook, reset the app in Settings > Apps. Your email stays safe on the server either way.
Applies to: Classic and new Outlook on Windows 10. Checked against Microsoft Support on September 28, 2026.
Before you start
- Clearing the cache doesn’t delete your emails, contacts or calendar. They’re stored with your email account.
- Close Outlook first, so it isn’t using the files.
Clear the cache in classic Outlook
- Close Outlook.
- Press Windows logo key + R, type %localappdata%\Microsoft\Outlook\RoamCache, and select OK.
- Press Ctrl + A to select everything, then press Delete.
- Open Outlook again. It rebuilds the cache.
To find the folder by hand, see how to open the AppData folder in Windows 10.
Clear the saved email suggestions
Outlook remembers addresses you’ve typed before. If it suggests old or wrong addresses:
- In classic Outlook, select File > Options > Mail.
- Under Send messages, select Empty Auto-Complete List, then Yes.
To remove just one address, start typing it in the To box and select the X next to it.
Reset the new Outlook
- Select Start > Settings > Apps > Apps & features.
- Select Outlook (new), then Advanced options.
- Select Reset. You may need to add your email account again. Then send a test email from your Windows 10 PC to confirm Outlook works.
Clear the attachment cache
When you open an attachment, classic Outlook saves a temporary copy in a hidden folder. It can fill up and cause “can’t create file” errors when opening attachments. Close Outlook, press Windows + R, paste %localappdata%\Microsoft\Windows\INetCache\Content.Outlook, and press Enter. Open the folder with the random name inside, delete its contents, and reopen Outlook. Save any attachment you edited somewhere else first, because edits made to an opened attachment only live in this folder.
Rebuild your offline mailbox
If clearing the cache didn’t help and you use a Microsoft 365, Outlook.com, or Exchange account, Outlook’s offline copy of your mailbox (the .ost file) may be damaged. Rebuilding it is safe because your mail is stored on the server:
- In classic Outlook, select File > Account Settings > Account Settings > Data Files.
- Select your account and choose Open File Location.
- Close Outlook, then rename the .ost file, for example by adding .old to the end.
- Open Outlook. It downloads a fresh copy, which can take a while for a large mailbox.
Don’t do this with a .pst file. PST files hold mail that may exist nowhere else.
If Outlook is still slow or crashing
Start it without add-ins to test: press Windows + R, type outlook.exe /safe, and press Enter. If it works well in safe mode, go to File > Options > Add-ins, select Go next to COM Add-ins, and turn them off one at a time to find the culprit. You can also repair Office from Settings > Apps, by selecting Microsoft Office, then Modify > Quick Repair.
Frequently asked questions
Outlook is still slow or crashing. What next?
Repair Office: right-click Start, select Apps and Features, select Microsoft 365 or Office, select Modify, and choose Quick Repair. For Online Repair, safe mode and profile fixes, see how to repair Outlook 365 in Windows 10.
Does this clear Teams too?
No. Teams has its own cache. See how to clear the Teams cache in Windows 10.
Will my signature be deleted?
No. Signatures are saved separately. See how to add a signature in Outlook on Windows 10.
Will clearing the cache delete my emails?
No. The cache only holds temporary data, such as display settings and recent lookups. Your messages, contacts, and calendar stay in your mailbox, and Outlook rebuilds the cache the next time it opens.
Microsoft’s reference is Manage suggested recipients in the To, Cc, and Bcc fields in Outlook. More help is on our Windows Help & Guides page.
Related: How to reset Outlook to default settings.
Related: How to change the Outlook view back to normal.
Related: how to configure Outlook in Windows 10.
Related: how to change the send and receive frequency in Outlook.
Matt Jacobs has been working as an IT consultant for small businesses since receiving his Master’s degree in 2003. While he still does some consulting work, his primary focus now is on creating technology support content for SupportYourTech.com.
His work can be found on many websites and focuses on topics such as Microsoft Office, Apple devices, Android devices, Photoshop, and more.