How to Clear Cache Data in Outlook

To clear cache data in Outlook, first identify which Outlook version you use: in classic Outlook for Windows, clear autocomplete suggestions or rebuild the local Exchange cache; in new Outlook, repair or reset the app; and in Outlook on the web, clear your browser’s cached files. These actions affect different kinds of local data, so use the option that matches the problem. Your mail stored on the server normally remains intact, but check that messages have synced and that you have internet access before resetting or rebuilding anything.

What You’ll Need

A working internet connection and access to the Microsoft 365 or mail account you use in Outlook.
A few minutes to let Outlook sync after the cache is cleared or rebuilt.
If you use classic Outlook with Exchange or Microsoft 365, confirm that important messages in the Outbox and Drafts have synced. Keep Outlook open and connected long enough to finish sending and receiving first.
For Outlook on the web, the name of your browser, such as Edge, Chrome or Safari. The browser’s clear-cache controls differ.

Step-by-Step

Identify which Outlook you are using. On Windows, classic Outlook has a File tab in the upper-left corner. New Outlook usually has a Settings gear and does not have the same File > Options layout. Outlook on the web runs in a browser at Outlook on the web. On a Mac, use the Outlook app and check its menu bar and Settings. This distinction matters: there is no single cache-clearing command that applies to every version.
Choose the cache related to the issue. If Outlook suggests old or incorrect recipient addresses, clear the autocomplete list. If a mailbox folder is missing recent mail or will not sync in classic Outlook for Windows, consider rebuilding its local Exchange cache. If the new Outlook app is frozen or displaying stale content, try Repair and then Reset if necessary. For a browser problem, clear cached files for the browser. Avoid clearing everything just in case; the least disruptive relevant option is usually best.
Clear autocomplete suggestions in classic Outlook for Windows, if that is what you mean by cache. Open Outlook and select File > Options > Mail. Under Send messages, select Empty Auto-Complete List, confirm, and select OK. This removes the stored recipient suggestions that appear as you type in the To, Cc or Bcc fields. It does not delete messages, contacts or entries in your address book. Outlook may build new suggestions as you send messages.
Rebuild the local Exchange cache in classic Outlook for Windows only when syncing is the problem. First, make sure Outlook shows that it is connected and allow pending messages to send and folders to sync. Close Outlook completely. Open Windows File Explorer, enter %LOCALAPPDATA%\Microsoft\Outlook in the address bar and press Enter. Find the .ost file associated with the affected account and rename it, for example by adding .old to its name. Do not delete or rename a .pst file. Reopen Outlook while connected to the internet; it should create a fresh OST and download the mailbox again. Large mailboxes may take a while to finish syncing, and some content may be unavailable until the download completes.
Check what the OST rebuild will affect before doing it. An OST is a local working copy for supported Exchange, Microsoft 365 and some IMAP accounts; it is not a general-purpose backup. Mail and calendar items already synced to the server can normally be downloaded again. Items that exist only on the computer, unsent messages, or recent edits that have not synced may not be recovered from the server. If you are unsure whether an item is online, do not rebuild the cache yet. Ask your organization’s IT administrator or make a suitable backup first. POP accounts commonly use PST data files, which are not the cache to clear.
Repair or reset new Outlook on Windows if the app itself is malfunctioning. Close Outlook. Open Start > Settings > Apps > Installed apps, find Outlook (new), select the three-dot menu, then Advanced options. If the option is available, select Repair first and reopen Outlook. If the issue remains, return to the same page and select Reset, then launch Outlook and sign in again if asked. Repair is the less disruptive first choice. Reset can remove local app data and preferences, so make sure anything important has synced before using it.
Clear the browser cache for Outlook on the web. Close other Outlook tabs first. In Microsoft Edge, open Settings > Privacy, search, and services > Clear browsing data > Choose what to clear. In Chrome, open Settings > Privacy and security > Delete browsing data. Select a suitable time range and choose Cached images and files; leave cookies and other site data unchecked if you want to avoid signing out of websites. Clear the data, reopen Outlook on the web and sign in if requested. Safari and other browsers have their own privacy settings, so follow the equivalent cached-files option for that browser.
On a Mac, clear only the affected folder’s local copy when the option is available. In Outlook for Mac, Control-click or right-click the affected mail folder and look for Properties or a folder cache option. If Empty Cache appears, choose it, confirm, and let Outlook sync the folder again. The menu can differ by Outlook version and account type; do not remove account files from Finder or use a Windows OST procedure on a Mac. If the folder does not offer that command, install available Office updates and try syncing the folder or restarting Outlook instead. For a persistent account-wide sync problem, contact your administrator or Microsoft support before removing and re-adding a work account.
Allow Outlook to resync and verify the result. Keep the app open and online. Check the affected folder, send a small test message if appropriate, and confirm that new mail arrives. A large mailbox or slow connection can make the first refresh seem incomplete. If you use shared mailboxes or work offline, allow those folders to finish updating too before deciding whether the cache-clearing step worked.

Common Mistakes

Deleting the wrong file: The Outlook folder may contain both OST and PST files. Do not delete a PST as a cache-clearing shortcut; it can hold mail and other data that may exist only on that computer. If you cannot tell which file belongs to the account, stop and ask IT for help.

Assuming every cache is email: Clearing autocomplete suggestions affects recipient recommendations, while clearing browser files affects the web app’s stored resources. Neither action is the same as rebuilding a desktop mailbox cache. Pick the specific data type that relates to your symptom.

Resetting before syncing: A reset or cache rebuild can remove local-only changes. Check the Outbox, Drafts and any folders used offline, and make sure Outlook has connected successfully before proceeding. Do not assume that a message visible on one device has already reached the mail server.

Clearing cookies unnecessarily: Cookies can keep you signed in and store site preferences. For a browser refresh, try clearing cached images and files alone first. Selecting cookies or site data may sign you out and require you to authenticate again.

Interrupting the first download: After an OST rebuild or app reset, Outlook may show fewer messages temporarily while it downloads data. Do not repeat the reset simply because the mailbox is not fully populated straight away.

Tips

Match the action to the symptom: wrong recipient suggestions point to autocomplete; stale or missing folders in classic Outlook may point to sync or an OST; a broken new Outlook app may call for Repair; and a web-only display problem may be resolved by clearing the browser’s cached files. If the same mailbox works in another device or in Outlook on the web, that can help show whether the issue is local to one app.

Keep Outlook connected while it syncs, especially after rebuilding a large mailbox. If you are on a metered or unreliable connection, wait until you have stable internet before starting. For a work or school account, your organization may manage Outlook settings or restrict app resets; check with the help desk if an option is missing or disabled.

Before changing local data, note any settings or account details you may need to restore. Make sure you know your sign-in method, including any multifactor authentication steps. Avoid third-party utilities that promise to clean Outlook cache files automatically; they may remove data you did not intend to clear.

Troubleshooting

The OST file is not visible: Confirm that Outlook is closed and that you entered the path in File Explorer’s address bar, not the Windows search box. Some folders or files may be hidden, and the account may not use an OST at all. Do not create or rename a file based on a guess; use Outlook’s account and data-file information or ask IT to identify the correct account file.

Outlook does not rebuild or sync: Check that the computer is online and that you can sign in to the account in a browser. Restart Outlook, then check its connection or sync status. If your organization’s service is experiencing an outage, a local cache reset will not fix it. For a work account, contact IT if authentication repeatedly fails or the mailbox remains disconnected.

Some messages or folders are still missing: Search Outlook on the web or another device to see whether the content is present on the server. Check filters, archive folders, deleted items and any folder-specific sync settings. If an item appears only in the local Outlook app and not elsewhere, avoid further resets and seek help recovering it.

Repair or Reset is unavailable: Confirm you selected Outlook (new) in Windows Installed apps, not classic Outlook or Microsoft 365 as a whole. If your device is managed, an administrator may control these options. Restart Windows, install available app updates, and contact the administrator if the menu remains unavailable.

The browser still shows an old page: Close all Outlook tabs, clear cached files for the correct browser profile, and reopen the site. Check whether a private window or another browser loads current mail. If it does, a browser extension or profile setting could be interfering; disable extensions temporarily one at a time rather than repeatedly clearing all browsing data.

Frequently Asked Questions

Will clearing Outlook’s cache delete my emails?
Clearing autocomplete suggestions or browser cached files does not delete mailbox messages. A rebuilt Exchange cache normally downloads server-synced mail again, but local-only or unsynced items can be at risk. Check sync status first.

How often should I clear Outlook cache?
There is no routine schedule. Clear or rebuild a cache only when a specific issue calls for it, such as incorrect autocomplete suggestions or persistent local sync trouble. Repeated cache clearing can waste time while Outlook downloads the same data again.

Is deleting the OST file safe?
It can be a troubleshooting method for a synced Exchange or Microsoft 365 mailbox, but it is not risk-free if changes have not reached the server. Close Outlook and rename the correct OST rather than deleting files indiscriminately. Never treat a PST as disposable cache.

Does clearing the cache remove my Outlook password?
Clearing autocomplete or browser cached files alone should not normally remove saved credentials. Resetting new Outlook or clearing browser cookies can prompt you to sign in again. Have your password and any required multifactor authentication method available.

Can I clear the cache in Outlook on my phone?
Mobile steps depend on whether you use Outlook for iOS or Android and on your device. Start by updating or restarting the app. If the app offers a reset or account-removal option, confirm that mail is synced and that you can sign in before using it; do not remove a work account without checking your organization’s instructions.

Why does Outlook use cache data?
A local cache helps desktop and mobile apps show mail and other mailbox information quickly, and can make some content available when connectivity is limited. Because it is a working copy rather than necessarily the only copy, it can often be rebuilt, but only after checking for unsynced changes.

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

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