Clear Cache in Microsoft Outlook: Windows, Mac & Web

To clear the cache in Microsoft Outlook, use the method for your version: empty the Auto-Complete list or rebuild the offline mailbox file in classic Outlook for Windows, empty a folder cache in classic Outlook for Mac, reset the new Outlook app, or clear cached files in your browser for Outlook on the web. Clearing cache can fix stale messages, display glitches, or loading problems; it does not normally delete mail stored on the server. Before you start, identify your Outlook version and make sure anything you need is synced or backed up.

What You’ll Need

A few minutes and access to the computer or browser where Outlook is having trouble.
Your Microsoft 365, Exchange, Outlook.com, or other email sign-in details in case the app asks you to sign in again.
A reliable internet connection if Outlook needs to download mailbox data again.
For Windows file cleanup, permission to close Outlook and access your Windows user files. Do not proceed with deleting a data file unless you can identify whether it is an OST or PST file.

Step-by-Step

Outlook does not have one universal Clear Cache button. Choose the section that matches your app. Classic Outlook is the desktop version with the File tab; new Outlook has a Settings gear and a different layout. Outlook on the web runs in a browser.

Check which Outlook you are using. On Windows, look for a File tab in the Outlook window: if it is present, you are likely using classic Outlook. If the app has a Settings gear and no File tab, it is likely new Outlook. On a Mac, check whether the app offers a Legacy Outlook switch; menu options differ between new and legacy versions. If you use Outlook in a browser, follow the web steps below.
Clear the Auto-Complete list in classic Outlook for Windows, if suggested names are the issue. Open Outlook and select File > Options > Mail. Under Send messages, select Empty Auto-Complete List, then confirm. This removes the stored suggestions that appear as you type recipients in the To, Cc, or Bcc fields. It does not clear messages, contacts, or the mailbox cache. Outlook will build new suggestions as you send mail. If you only want to remove one incorrect suggestion, start a new message, type enough of the address to show the suggestion, then select the X beside that suggestion rather than emptying the entire list.
Rebuild the offline mailbox cache in classic Outlook for Windows only when mail is stale or syncing incorrectly. An Exchange, Microsoft 365, or Outlook.com account using Cached Exchange Mode stores a local OST file so you can work offline. First make sure Outlook has finished sending and receiving, and check Outlook on the web or another device to confirm that important recent messages and changes are present. Items that exist only on this computer may not be restored after rebuilding the cache.
Close classic Outlook completely before working with its OST file. Exit the app and wait briefly. Press Windows key + R, enter %LOCALAPPDATA%\Microsoft\Outlook, and press Enter. Find the OST file associated with the affected account. If you are unsure which file belongs to the account, stop rather than guessing. You can rename the OST file by adding a suffix such as .old, which makes it easier to restore if needed; do not rename or delete a PST file. When Outlook starts again, it should create a fresh OST and synchronize mailbox data from the server. The first sync can take a while, especially for a large mailbox.
Use a new Outlook profile instead if you cannot safely identify the OST file. In Windows, close Outlook and open Control Panel. Search for Mail, open the Mail setup item, then choose Show Profiles and Add to create a profile. Add the affected account and follow the prompts. When the new profile is ready, set Outlook to prompt for a profile or make the new one the default in the same profile window. Keep the old profile until you confirm the new one has synced and contains the expected mail. Profile labels can vary slightly depending on the Office installation.
Empty a folder cache in legacy Outlook for Mac. In Outlook, locate the affected mail folder in the sidebar, Control-click or right-click it, and choose Properties. If the dialog offers Empty Cache, select it and confirm. Outlook will fetch the folder contents again from the mail server; allow time for the folder to repopulate. Use this for a particular folder that looks out of date, not as a routine cleanup. The command may not be available in new Outlook for Mac or for every account type.
For new Outlook on Windows, repair or reset the app through Windows settings. Close Outlook, open Settings > Apps > Installed apps, find Outlook (new), and open its advanced options if shown. Choose Repair first; this attempts to fix the app without the more disruptive reset. If the problem remains, choose Reset and confirm. The reset clears app data and may require you to sign in and set preferences again. Mail stored on the server should sync back after sign-in, but check that any local-only content is safe before resetting.
Clear browser cache for Outlook on the web. In Microsoft Edge, open Settings > Privacy, search, and services > Clear browsing data > Choose what to clear. In Google Chrome, open Settings > Privacy and security > Delete browsing data. Select a time range that includes when the issue began and select cached images and files. You usually do not need to clear browsing history. Clearing cookies and site data can sign you out of Outlook and other websites, so leave those options unchecked unless you specifically need to reset the sign-in session. Close and reopen the browser, then sign in again if asked.
Check whether the problem is fixed. Open the affected folder or message, send or receive a small test message if appropriate, and confirm the expected data is present. Give a rebuilt mailbox time to synchronize before deciding that messages are missing. If only the display remains wrong, refresh Outlook or restart the app before trying a more extensive reset.

Common Mistakes

Deleting the wrong data file: An OST is generally a replaceable offline copy of a server mailbox, while a PST can contain mail or archives stored locally. Do not delete a PST to clear cache. If you cannot tell which file you have, use the app’s repair options or ask your IT administrator.

Assuming every cache is the same: The Auto-Complete list stores recipient suggestions; an OST stores an offline mailbox copy; browser cache stores website files. Clearing one will not fix problems caused by another. Match the action to the symptom.

Resetting before checking sync: A rebuild can take time, and local changes that have not reached the server can be at risk. Confirm sync status and check the mailbox online before removing or resetting local data.

Clearing all browser data unnecessarily: Removing cookies can sign you out, and clearing saved passwords or browsing history is not required to refresh Outlook’s cached files. Select only cached images and files unless troubleshooting specifically calls for more.

Expecting instant results: A new offline cache has to download mailbox content. Outlook may look incomplete while the download is in progress, particularly with a large mailbox or slow connection.

Tips

Use the least disruptive fix first. For a wrong recipient suggestion, remove that one suggestion. For a single stale folder in legacy Outlook for Mac, empty that folder’s cache. Try repairing new Outlook before resetting it. Rebuild an OST only when the problem points to a damaged or outdated offline mailbox copy, not just because Outlook is using disk space.

Keep Outlook open and connected during a full resync, and avoid putting the computer to sleep if the download is still underway. If your organization manages Outlook, check with IT before changing profiles or resetting the app; company policies, shared mailboxes, and archived data can affect the right procedure. After a successful repair, confirm that sent messages, calendar items, and shared folders are also syncing as expected.

On a work or shared computer, consider whether clearing browser cookies will affect other people’s sessions. In a browser, you can often try a private window first to see whether the issue is limited to the existing browser profile. That test does not clear the stored cache, but it can help distinguish a browser-profile problem from an account or service problem.

Troubleshooting

Outlook will not reopen after closing it: Check Task Manager on Windows to see whether an Outlook process is still running. If it is, wait for it to finish or close it normally before changing an OST file. Restarting the computer can release a file that is still in use.

The mailbox does not repopulate after an OST rebuild: Confirm the computer is online, then check that the account signs in successfully. In classic Outlook, use Send/Receive > Update Folder or Send/Receive All Folders to prompt an update. Large mailboxes may need substantial time. If Outlook reports an authentication or server error, resolve that issue before rebuilding the cache again.

New Outlook’s Reset option is missing: Confirm you are viewing the Windows Settings page for the installed app, not Outlook’s own settings. Some managed devices hide advanced options. Try Repair if available, restart Windows, and contact your administrator if the controls are restricted. Do not uninstall the app as a first step.

Empty Cache is not available on Mac: The command depends on the Outlook edition, account, and folder. Make sure you are using legacy Outlook and have selected a mail folder, rather than a message. If you are using new Outlook, update the app and restart it; avoid removing the account unless you have verified that important data is stored on the server and can be downloaded again.

Clearing browser files did not help: Reload Outlook on the web, sign out and back in, and try a private browsing window. If Outlook fails in multiple browsers or on another device, the issue may be with the account, network, or Microsoft 365 service rather than the local cache. Check your organization’s service-status notices or contact its support team.

Frequently Asked Questions

Will clearing Outlook cache delete my emails?
Usually, no. Mail in a server-based mailbox can be downloaded again. However, unsynced changes or items stored only in a local PST may not be recoverable from the server, so verify those before removing data files.

How often should I clear the Outlook cache?
There is no routine schedule. Clear or rebuild a cache when a specific problem calls for it, such as stale folder contents or a damaged local app state. Frequent clearing can cause repeated downloads and sign-ins without improving performance.

Does emptying Auto-Complete remove my contacts?
No. It removes the saved recipient suggestions that appear while you type. Your address book and saved contacts are separate. Outlook creates new suggestions again as you send messages.

How long does an Outlook cache rebuild take?
It depends on mailbox size, connection speed, and whether shared folders are included. Basic folders may appear first while older messages continue downloading. Keep Outlook connected and check sync status before treating missing items as lost.

Can I clear the cache in Outlook on my phone?
Outlook for iOS and Android does not use the same desktop OST controls. Restart the app and check for updates first. If problems continue, use the phone’s app settings to clear app data only if you understand that you may need to sign in and allow the mailbox to sync again; exact controls differ by device.

Is clearing cache the same as repairing Outlook?
No. Clearing or rebuilding cache removes or refreshes local stored data. Repairing an app attempts to fix its installation. For new Outlook on Windows, use Repair before Reset; for classic Outlook, an OST rebuild affects the offline mailbox copy rather than reinstalling Office.

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