How to Clear the Outlook Cache in Windows 10

To clear the Outlook cache on Windows 10, close Outlook, press Windows + R, type %localappdata%\Microsoft\Outlook\RoamCache, and press Enter. Select the files in that folder and delete them, then reopen Outlook. This clears temporary settings and data that can make Outlook slow, show old information, or behave oddly. If you want to keep your email address suggestions, skip any file with Autocomplete in its name.

These steps are for classic Outlook for Microsoft 365, 2021, 2019, and 2016. Below you’ll also find how to rebuild Outlook’s offline mail cache, clear AutoComplete, and reset the new Outlook app.

What “clearing the Outlook cache” means

Cache	What it stores	Clear it when
RoamCache folder	Temporary settings, calendar and signature data, AutoComplete	Outlook is slow, crashes, or shows outdated info
Offline mail file (.ost)	A local copy of your mailbox	Emails are missing, won’t sync, or search is broken
AutoComplete list	Email address suggestions in the To box	Old or wrong addresses keep appearing
Secure temp folder	Attachments you’ve opened	Attachments won’t open or save

Clear the RoamCache folder

1. Close Outlook completely. Check the notification area to make sure it isn’t still running.
2. Press Windows + R, paste %localappdata%\Microsoft\Outlook\RoamCache, and press Enter.
3. Press Ctrl + A to select all files. To keep your AutoComplete suggestions, hold Ctrl and click any Stream_Autocomplete file to deselect it.
4. Press Delete.
5. Reopen Outlook. It rebuilds the files it needs automatically.

Rebuild the offline mail cache (.ost file)

If you use a Microsoft 365, Outlook.com, or Exchange account, Outlook keeps a copy of your mailbox in an .ost file. Rebuilding it downloads a fresh copy from the server. Your email stays safe on the server.

1. In Outlook, go to File > Account Settings > Account Settings > Data Files tab.
2. Select your account and click Open File Location. Note the .ost file’s name.
3. Close Outlook.
4. Rename the .ost file, for example by adding .old to the end.
5. Open Outlook. It creates a new .ost file and downloads your mail, which can take a while for large mailboxes.
6. Once everything looks right, delete the old file.

Don’t do this for POP accounts that store mail in a .pst file. A .pst file may be the only copy of your email.

Clear the AutoComplete list

• Remove one address: Start typing it in the To box, point to the suggestion, and click the X.
• Remove all suggestions: Go to File > Options > Mail, scroll to Send messages, and click Empty Auto-Complete List.

Clear the attachment temp folder

Outlook stores opened attachments in a hidden temporary folder, which can fill up and cause “can’t create file” errors. To find it, open Registry Editor and go to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security. The OutlookSecureTempFolder value shows the path. Close Outlook, open that folder, and delete its contents.

Reset the new Outlook for Windows

The new Outlook app doesn’t use RoamCache or .ost files the same way. If it’s misbehaving:

1. Close the app.
2. Go to Settings > Apps > Apps & features and find Outlook (new).
3. Click it, choose Advanced options, and click Repair. If that doesn’t help, click Reset. You’ll need to sign in again.

Keep the mailbox small by emptying Deleted Items on exit.

Frequently asked questions

Will clearing the Outlook cache delete my emails?

No. Clearing RoamCache doesn’t touch your email. Rebuilding an .ost file is also safe for Microsoft 365, Outlook.com, Exchange, and IMAP accounts because your email is stored on the server.

How often should I clear the Outlook cache?

Only when you have a problem. Outlook manages its cache on its own the rest of the time.

Why is Outlook still slow after clearing the cache?

Try starting it in safe mode with outlook.exe /safe from the Run box to check for problem add-ins, and run File > Office Account > Update Options > Update Now.