How to Clear Outlook Cache on Windows Without Losing Mail
Outlook taking up disk space and Outlook suggesting the wrong recipient are different problems. Classic Outlook keeps a mail database as well as an autocomplete cache, while new Outlook for Windows has its own web cache and offline storage. Clearing the wrong folder can remove useful local data without solving either problem.
Identify the Data Before Clearing It
These steps cover Windows 11 and Windows 10. Menu routes below use Microsoft's English labels so you can match them to your interface. First check which Outlook you are using, then choose the row that matches your problem.
| Data | Location | First Action | What You Lose |
|---|---|---|---|
| Classic recipient cache | %LOCALAPPDATA%\Microsoft\Outlook\RoamCache |
Remove the wrong suggestion in Outlook | Remembered recipient suggestions if the list is cleared |
| Classic offline mail | .ost under %LOCALAPPDATA%\Microsoft\Outlook |
Reduce the offline mail period | Offline access to older mail outside that period |
| Personal mail archive or POP data | .pst, commonly under Documents\Outlook Files |
Keep and back up | Potentially the only copy of mail if deleted |
| New Outlook network cache | %LOCALAPPDATA%\Microsoft\Olk\EBWebView\Default\Cache |
Clear the browser cache as described below | Cached resources must download again |
| New Outlook settings and offline data | Other contents of %LOCALAPPDATA%\Microsoft\Olk and its package folder |
Adjust offline settings, consider Repair for faults | Reset can remove local data and require sign-in |
Microsoft distinguishes mail data files and their locations. Check your actual classic Outlook file under File > Account Settings > Account Settings > Data Files, where the account and path are listed. Do not delete a whole Outlook folder or any .pst as a cache-clearing shortcut.
Classic Outlook: Fix Recipient Suggestions First
For one wrong address, create a message, type enough of the address to show the suggestion, then use its X or the Delete key. To clear the entire legacy list, use File > Options > Mail > Send messages > Empty Auto-Complete List, then confirm. This removes remembered suggestions, not a mail archive.
Microsoft's autocomplete guidance has an important exception: with Exchange Online, Outlook for Microsoft 365 version 2202, build 14931.20604, and later uses Microsoft Search for recipient suggestions. Its full-list clearing instructions do not apply to that scenario. Removing one suggestion is the relevant starting point.
The older nickname-cache documentation places a temporary local copy in RoamCache for Outlook 2010/2013, with the authoritative stream stored in the mailbox. That is why deleting RoamCache is neither a universal suggestion reset nor a sensible way to recover gigabytes. Keep it unless you are following a repair procedure for your specific version.
Classic Outlook: Reduce Offline Mail Instead of Deleting It
For an Exchange or Microsoft 365 account using Cached Exchange Mode, open File > Account Settings > Account Settings, select the account and choose Change. Under Offline Settings, reduce the Mail to keep offline slider to a period you actually need, then complete the dialog and let synchronization finish. Older messages remain on the server but need an online connection to access. This slider is not a general POP archive control.
Microsoft's offline guide covers both Outlook versions. For new Outlook, use Settings > General > Offline to choose folders and the number of days retained locally. Adjust the relevant account rather than deleting its storage.
If the classic data file stays large, Microsoft documents compaction. Open File > Account Settings > Account Settings > Data Files, select the file and Settings. For Exchange or Outlook.com, continue through Advanced > Outlook Data File Settings, then choose Compact Now. Compaction reclaims unused space inside the file, not mail you still want. Avoid deleting messages just to make this button useful.
New Outlook: Clear the Web Cache, Then Consider One Folder
For stale web resources or add-in content, Microsoft's Office cache instructions give a new Outlook procedure. Close Outlook, open Command Prompt and run:
olk.exe --devtools
This launches Outlook and Microsoft Edge DevTools. In DevTools, select Network, right-click the Requests table and choose Clear browser cache. Close both windows, reopen Outlook normally and repeat the action that failed. This is documented for the web/add-in cache, not as a cure for mailbox synchronization or every startup failure. If the command is unavailable, use the repair route below rather than guessing an executable path.
For manual cleanup, quit Outlook completely, then paste this exact path into File Explorer's address bar:
%LOCALAPPDATA%\Microsoft\Olk\EBWebView\Default\Cache
If it exists, remove only its contents using ordinary Delete and leave adjacent folders alone. Skip locked items instead of forcing removal. If it does not exist, stop rather than substituting the whole Olk folder.
Microsoft's VDI folder map identifies this folder as cached network-call content that downloads again. The same map identifies IndexedDB, Local Storage and Attachments as user and app data, so do not sweep those folders with it. Its roaming-exclusion advice is not permission to delete all profile data.
Use Repair Before Reset for New Outlook Faults
On Windows 11, open Settings > Apps > Installed apps, find new Outlook and use its menu to open Advanced options. Windows 10 uses Settings > Apps > Apps & features, then the app and Advanced options. Select Repair if available and test again. Microsoft's repair instructions place Reset after Repair fails or is unavailable.
Treat Reset as a local-data reset, not a cache-only button. Before using it, confirm important mail, drafts and sent items are present in webmail, preserve anything still only on this PC, and make sure you can sign in again. Do not reset just to make a storage number smaller.
Check Both the Result and the Space
Reopen Outlook, check the original symptom, open a recent and an older message, and test the offline period you chose. Compare the same folder's size and the same drive's free space before and after.
If space has not returned, files moved to the Recycle Bin still occupy the drive. Keep them available for recovery until the result is checked. An .ost may also need compaction, while a web cache will grow again during normal use. A renewed download is expected when you reopen uncached content.
If sign-in is lost, sign in to the same account and verify webmail before changing more folders. If local drafts are missing, stop further cleanup and check retained copies or backups. Clearing cache cannot recover unsynchronized work.
Where Mole Fits
Mole for Windows currently has no Outlook-specific row in Clean, including RoamCache, .ost, .pst or Olk, so there is no Outlook row selected or waiting unticked for review. This describes Clean, not uninstalling Outlook or manually deleting files elsewhere. Use Outlook's controls for this task. For other storage, see Windows cache cleanup and finding large files.
FAQ
Can I Delete an OST File to Free Space?
Not as routine cleanup. Microsoft describes rebuilding an Exchange OST for repair, but Outlook downloads the server data again. Verify synchronization and protect local-only work first, then prefer reducing offline retention for lasting savings.
Is a PST File Just Another Cache?
No. It can contain a POP mailbox or a personal archive with no server copy. Keep it and make an independent backup before any repair or storage change.
Will Clearing Cache Fix a Full Mailbox Warning?
Local cache and the server mailbox quota are different. Removing cached resources does not remove server mail. Check the account's mailbox storage separately rather than repeatedly deleting local folders.