Clear Cache in Microsoft Outlook: Windows, Mac & Mobile

To clear cache in the Microsoft Outlook app, use the method for your device: repair or reset new Outlook in Windows settings, rebuild a server-based Outlook data file in classic Outlook, reset an account on Mac, or clear the app cache on Android. On iPhone, reinstalling the app is the closest equivalent. Cache clearing can refresh stale data or fix app glitches, but it is not the same as deleting email; check that important messages are synced before resetting or reinstalling.

Outlook does not have one universal “Clear cache” button. The app stores different kinds of temporary data depending on its version and device. Follow only the section that matches your setup, and start with the least disruptive option.

What You’ll Need

Your device and Outlook version: new Outlook for Windows, classic Outlook for Windows, Outlook for Mac, or the Android or iPhone app.
A reliable internet connection so Outlook can download current mail and settings after a reset.
Your Microsoft 365, work, or email-account sign-in details, including any required multifactor authentication method.
A moment to confirm that recent messages and drafts are synced. If you use a POP account, a local-only folder, or a PST file, back it up before removing or rebuilding data files.

Step-by-Step

First identify which Outlook you use. On Windows, “new Outlook” is the newer app, while “classic Outlook” is the traditional desktop program with the full ribbon and File tab. Their cache controls are different.

For new Outlook on Windows, try Repair first. Close Outlook. Open Windows Settings, then choose Apps > Installed apps (called Apps & features in some Windows versions). Find Outlook (new), select the three-dot menu, and choose Advanced options. If there is a Repair button, select it and wait for Windows to finish. Repair attempts to fix the app without clearing its stored data. Open Outlook and check whether the original problem is gone.
If Repair does not help, reset new Outlook. Return to the same Advanced options page and select Reset, then confirm. Reset clears the app’s local data and settings. Launch Outlook, sign in again if prompted, and allow it to sync. Mail kept in Microsoft 365, Exchange, Outlook.com, or another server-based account should download again, but local-only content and unsynced drafts may not. Do not use Reset until you have checked for anything important that exists only on the device.
For classic Outlook on Windows, clear only the autocomplete cache if suggestions are the issue. Close Outlook completely. Press Windows key + R, enter %LOCALAPPDATA%\Microsoft\Outlook\RoamCache, and press Enter. In the folder that opens, locate the files with names beginning Stream_Autocomplete. Delete those autocomplete files, not every file in the folder. Reopen Outlook; it will create new autocomplete data as you use it. This removes suggested recipient entries, so names you previously selected may need to be typed again. It does not clear the mailbox or repair a stale message list.
For classic Outlook, rebuild an offline mailbox cache only when mail is not syncing or displaying correctly. First confirm the account is server-based, such as Microsoft 365, Exchange, Outlook.com, or IMAP, and that its recent mail is visible in webmail. In Outlook, select File > Account Settings > Account Settings, open the Data Files tab, select the relevant data file, and choose Open File Location if available. Note the file name and location, then exit Outlook fully. In File Explorer, rename the matching .ost file by adding something like .old to its name. Reopen Outlook and let it rebuild and resync the offline cache; this can take a while for a large mailbox. If Outlook does not recreate the file or the account is not clearly server-backed, stop and contact your administrator rather than deleting more files. Never rename or delete a .pst file as a cache-clearing step: it may contain the only copy of local mail.
For Outlook on Mac, reset the affected account. In Outlook, open Tools > Accounts, select the account with the problem, then choose the … menu and Reset Account, if that command is available. In some versions, account controls are under Outlook > Settings > Accounts; select the account and look for its reset or manage option. Confirm the reset and allow Outlook to reconnect and download data. This refreshes the local account cache, but it may remove unsent or locally stored items. If you cannot find a reset command, update Outlook and consult your organization’s support team rather than removing account files by hand.
For Outlook on Android, clear the app cache through Android settings. Close Outlook, then open the phone’s Settings > Apps (the label may be Apps & notifications), select Outlook, choose Storage & cache or Storage, and tap Clear cache. The exact wording varies by phone manufacturer. Reopen Outlook and wait for it to refresh. Choose Clear storage or Clear data only if you intend to reset the app completely; those options can remove account settings and require you to sign in again.
For Outlook on iPhone or iPad, remove and reinstall the app if a refresh is needed. iOS does not provide a separate Outlook cache-clearing button. Check first that your account is syncing and that you know your sign-in details. Touch and hold Outlook, choose Remove App > Delete App, then reinstall Microsoft Outlook from the App Store and sign in. Deleting the app removes its local data. Server-synced messages should return after sign-in, but unsynced drafts or device-only data may not.
Let Outlook finish syncing, then test the original problem. Connect to Wi-Fi or a stable network, open the relevant folder, and give the app time to download messages and attachments. Send a test message or check whether the stale item updates. A temporarily empty folder or slower first launch can be normal while the cache is rebuilt.

Common Mistakes

Deleting the wrong Outlook file: An .ost file is generally a rebuildable offline copy for a server-based account; a .pst can hold mail stored only on that computer. Do not treat the two as interchangeable. If a file’s purpose is unclear, leave it alone.

Expecting cache clearing to fix every mail problem: Clearing local data will not correct a wrong password, expired account, full mailbox, server outage, or incorrect mail rule. Check whether the same messages appear in webmail before changing local files.

Confusing Windows Repair with Reset: Repair is the less disruptive first option. Reset removes local app data and may mean signing in and setting preferences again. Read the confirmation prompt before proceeding.

Assuming drafts are always backed up: A draft that has not synced, a message in an offline folder, or mail stored in a local data file may not exist on the server. Open the draft and confirm it is available online or copy its contents somewhere safe first.

Clearing all browser data for the Outlook app: Browser cache controls do not normally clear the installed Outlook app’s cache. If you actually use Outlook on the web, clear site data for the Outlook website only if needed; this may sign you out and remove site preferences.

Tips

Use the narrowest fix that matches the symptom. Recipient suggestions point to autocomplete data; missing or stale mailbox content may point to a sync or offline-cache issue; crashes in new Outlook may justify Repair.
Make a note of the account address and any special settings before resetting. Work or school accounts may require your organization’s sign-in approval or device-management setup.
Keep the device online during the first sync, and avoid repeatedly closing Outlook while it is rebuilding. Large mailboxes and attachments can take considerable time to reappear.
Update Outlook and your operating system after the refresh. A cache reset can clear corrupted local data, but an app update may be needed to prevent the same fault from returning.
If several people on the same organization are affected at once, ask the Microsoft 365 administrator to check service health before rebuilding individual devices.

Troubleshooting

The cache folder or file is not there: Make sure Outlook is closed, confirm you opened the correct Windows profile, and check that hidden items are visible in File Explorer. Folder names and data locations vary by account type and Outlook version. Do not create a replacement file manually. If you cannot identify the correct file, skip the manual step.

Outlook asks for a password after reset: This is expected when local sign-in data has been removed. Enter the account password and complete multifactor authentication. If the password is rejected, verify it by signing in to the account’s official webmail page; for a work account, contact your administrator before changing saved credentials repeatedly.

Mail is still missing after the cache rebuild: Check webmail and the Deleted Items, Archive, Junk Email, and other folders. If the message is absent online too, the issue is probably not just the local cache. Check account filters, retention policies, or service status, and ask your administrator or email provider for help.

The first sync seems stuck: Confirm the device has internet access, Outlook is not in an offline mode, and there is enough free storage. Restart Outlook once, then allow time for a large mailbox to download. On a managed work device, a VPN or organization policy may be required to connect.

The app still crashes or behaves badly: Install available Outlook and system updates. For new Outlook on Windows, try Repair if you have not already; Reset is a later option. On a phone, restart the device and reinstall only after confirming your account data is synced. If the problem affects one account only, remove and add that account only when you know the credentials and any setup requirements.

You use Outlook in a browser rather than an installed app: Refresh the page and sign out and back in first. If the issue persists, clear site data for the specific Outlook web address in your browser settings, then sign in again. Avoid clearing all browser cookies unless necessary, as that signs you out of other websites too.

Frequently Asked Questions

Will clearing Outlook’s cache delete my emails?
Usually, server-synced email remains on the mail server and downloads again after Outlook reconnects. However, unsynced drafts, local-only folders, and PST contents may be at risk. Confirm what is stored online before resetting or removing files.

How often should I clear the Outlook cache?
There is no routine schedule. Clear or rebuild cache data only to address a specific problem, such as stale content, a sync fault, or an app that will not behave normally. Repeated resets create extra syncing and sign-in work without a guaranteed benefit.

Does clearing cache remove my Outlook password?
It can, especially when you reset the app or delete and reinstall it. Keep your password and multifactor authentication method available. A targeted Android “Clear cache” action is different from “Clear storage” or “Clear data,” which is more likely to reset sign-in details.

Why did my autocomplete suggestions disappear?
Classic Outlook’s autocomplete suggestions are separate from the mailbox cache. Deleting its Stream_Autocomplete files clears those saved suggestions, so Outlook has to build them again as you address new messages. This does not delete contacts from your address book.

Is clearing cache the same as removing and adding an account?
No. Clearing or rebuilding local cache data refreshes a local copy; removing an account changes Outlook’s account setup and can also remove local data. Try the least disruptive option first, and confirm that important messages are synced before removing an account.

Can I clear Outlook’s cache without internet access?
You can perform some local actions offline, but Outlook cannot download current server data until the device reconnects. Avoid resetting or rebuilding a cache when offline if you have unsynced work; first connect and confirm that drafts and recent changes have synchronized.

Try it: the Date Difference Calculator: days, months, years and weekdays between two dates, with the DATEDIF formulas.

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