Clear Outlook Cache: Find the Path and Remove It Safely

In classic Outlook for Microsoft 365 on Windows, the main offline cache is usually an OST file in %LOCALAPPDATA%\Microsoft\Outlook. To clear or rebuild that cache, close Outlook first, then remove the relevant OST file only after confirming the mailbox is synced; Outlook can recreate it from the mail server. Other Outlook caches, such as autocomplete data, have different locations and safer clearing controls.

What Outlook means by cache

Outlook uses local files to make mail and calendar information available quickly, including when a network connection is slow or unavailable. The word cache can refer to several kinds of stored data, though, and they are not interchangeable. The right cleanup depends on what you are trying to fix: a large offline mailbox file, stale recipient suggestions, or a problem with the Outlook app itself.

For a Microsoft 365 or Exchange account in classic Outlook, the principal offline store is typically an OST file. Outlook synchronizes its contents with the mailbox on the server. A separate PST file, by contrast, is commonly used for archives or mail stored only on the computer. Deleting a PST can permanently remove the only copy of that information, so do not treat every Outlook data file as disposable cache.

Autocomplete suggestions and temporary application data are separate again. Clearing one type of cache will not necessarily fix another. For example, rebuilding an OST may refresh mailbox data but is not the standard way to erase old recipient suggestions.

Find the classic Outlook cache path

The usual location for classic Outlook data files on Windows is:

%LOCALAPPDATA%\Microsoft\Outlook

To open that folder, press Windows key + R, enter the path, and press Enter. Windows expands the environment variable for the signed-in user and opens the corresponding local AppData folder. You can also paste the path into File Explorer’s address bar. AppData is hidden by default, so using the variable is often easier than browsing to it manually.

The folder can contain OST files, PST files, and other Outlook-related data. The file name may be based on an email address or profile, but names vary. To check the file Outlook is actually using, open classic Outlook and select File > Account Settings > Account Settings. On the Data Files tab, select an entry and choose Open File Location, if available. This helps distinguish the active mailbox store from an unrelated old file.

Another way to identify the active account is to select it in the Account Settings window and inspect its account and data-file details. Do not assume the newest or largest file is the right one to remove. If Outlook is open, a data file may be locked, and changing or deleting it at that point can cause errors.

Know which file you are about to clear

OST: An offline cache associated with supported Exchange, Microsoft 365, or IMAP account setups. It is generally rebuildable when the account’s data is safely synchronized, but it may contain changes that have not reached the server.
PST: A personal data file often used for archives, imports, or mail kept locally. It may be the sole copy of some messages, so do not delete it as a cache-cleaning shortcut.
Autocomplete data: The list of suggested recipients that appears as you type an address. Use Outlook’s autocomplete control rather than deleting mailbox files.
New Outlook app data: Data managed by the newer Outlook for Windows app. Its storage and repair options differ from those of classic Outlook.

File extensions are important clues, but they are not a substitute for checking the account configuration. If you are unsure whether a file is an OST or PST, or whether it contains locally stored messages, stop and make a backup or ask your organization’s support team before removing anything.

Rebuild an OST in classic Outlook

Rebuilding the offline cache can help when Outlook’s local copy appears damaged or out of date. It is not a routine maintenance task: after the file is removed, Outlook must download the mailbox again, which can take time and use network bandwidth. For a large mailbox, allow the synchronization to finish before judging whether the problem is resolved.

Open Outlook and check that it is connected. For important mail, calendar items, and contacts, confirm that recent changes are visible in Outlook on the web or another server-connected view. Resolve any synchronization errors first.
Close Outlook. Wait a moment, then check Task Manager to make sure Outlook is no longer running. Do not delete an open or actively used data file.
Open %LOCALAPPDATA%\Microsoft\Outlook and identify the OST file associated with the account. If you used Account Settings to locate the file, verify its extension and account before proceeding.
For a cautious approach, move the OST to a temporary backup folder rather than immediately deleting it. Do not move or remove a PST as part of this process.
Start Outlook again. For an account that supports an OST cache, Outlook should create or download a fresh local copy. Keep Outlook connected while it synchronizes, and check for missing or unsent items before removing the backup.

If Outlook reports that the file is in use, close Outlook completely and check for another Outlook process before trying again. If Outlook does not recreate the cache, or it continues to use the old file, do not repeatedly delete files at random. The account may use a different data-file arrangement, or the profile may need repair by your organization’s administrator.

Clear autocomplete suggestions separately

If the issue is an incorrect name or an old email address appearing while you type in the To field, clearing the OST is unnecessary. In classic Outlook for Microsoft 365 on Windows, use File > Options > Mail. Under the section for sending messages, select Empty Auto-Complete List and confirm. Outlook will build suggestions again as you address new messages. You can also remove an individual suggestion from the dropdown when it appears, rather than erasing the whole list.

Autocomplete controls and storage can vary between classic Outlook, new Outlook, and organization-managed accounts. In some setups, recipient suggestions may be influenced by saved contacts or directory results as well as the local suggestion list. Clearing autocomplete therefore may not remove a person from the company directory or from your Contacts folder.

New Outlook for Windows uses different controls

New Outlook for Windows is a separate app experience from classic Outlook, so the classic OST instructions should not be applied automatically. Its local app data is commonly associated with %LOCALAPPDATA%\Microsoft\Olk, but manually deleting files in an application data folder is a blunt step and can remove local app state or require the account to be set up again.

For a new Outlook problem, first close and reopen the app, check for updates, and use Windows’ app repair controls if needed. In Windows 11, go to Settings > Apps > Installed apps, find Outlook (new), open its advanced options, and choose Repair if that option is available. Repair is intended to address app problems without the more extensive consequences of a reset. A reset can clear app data and may require you to sign in or configure the account again, so use it only when simpler steps fail and you know your account credentials.

Exact labels can differ by Windows release and app version. If the app is managed by work or school, follow your IT team’s instructions before resetting it. Do not confuse Outlook (new) with classic Outlook, which may appear as Outlook (classic) or simply Outlook in Microsoft 365 installations.

Before clearing anything: safety checks

A cache is often replaceable, but only if the information it represents has been saved somewhere else. Mail that is still in the Outbox, changes made offline, or items in a local-only folder may not have synchronized. A safe cleanup starts by confirming the account type and synchronization state, not by deleting the largest file.

Check Outlook’s connection status and resolve any sync errors before rebuilding a mailbox cache.
Confirm that recent messages and calendar changes appear in Outlook on the web or another view of the server mailbox.
Keep PST files and any files whose purpose is unclear. Make a backup before changing data-file locations.
On a work computer, check with IT; retention policies, shared mailboxes, and managed profiles can affect what is safe to remove.
Expect a fresh OST to take time to download. Large mailboxes and slow connections can make Outlook seem incomplete while synchronization is still underway.

Cached Exchange Mode offers a useful control over how much mail is stored offline. In classic Outlook, open File > Account Settings > Account Settings, select the Exchange or Microsoft 365 account, choose Change, and look for Use Cached Exchange Mode and the mail-to-keep-offline slider. The exact controls depend on the account and Outlook configuration. Adjusting the slider changes the offline range; it is not the same as clearing the cache, and it does not delete the server mailbox.

Common problems and what they mean

The folder looks empty. The AppData path may have been entered for a different Windows user, or the account may store its active data elsewhere. Use Account Settings to locate the active data file rather than searching the entire drive and guessing.

Outlook says the file cannot be deleted. Outlook may still be running in the background, or another process may have the file open. Close Outlook fully and check Task Manager. Avoid forcing deletion while the file is in use.

Mail is missing after rebuilding. Synchronization may still be in progress, or the missing item may have existed only in the old local file. Check the server mailbox and any backups. This is why confirming synchronization and retaining the old OST temporarily are sensible precautions.

The problem comes back. A cache rebuild cannot repair a server-side issue, a damaged Outlook profile, a faulty add-in, or a network problem. If the issue persists, record any error message and contact support rather than repeatedly deleting the cache.

Frequently Asked Questions

What is the default Outlook cache path in Windows?
For classic Outlook, the usual location is %LOCALAPPDATA%\Microsoft\Outlook. Use Account Settings to verify the active file, because profiles and account types can differ.

Can I delete the Outlook OST file?
Usually, an OST for a properly synchronized Exchange, Microsoft 365, or IMAP account can be rebuilt by Outlook. Close Outlook first, verify recent work is synchronized, and do not delete a PST or an unidentified file.

Will clearing the OST delete emails from the server?
Removing a synchronized OST does not normally delete the server mailbox; Outlook downloads a new local copy. However, unsynchronized changes or local-only data may be lost, so verify the server copy before proceeding.

How do I clear old recipient suggestions?
In classic Outlook, select File > Options > Mail > Empty Auto-Complete List. For one unwanted suggestion, remove that entry from the suggestion dropdown when it appears.

Is the Outlook cache path the same in new Outlook?
No. New Outlook is a different Windows app and commonly uses an app-data location under %LOCALAPPDATA%\Microsoft\Olk. Prefer Windows’ Repair or Reset controls over manually deleting files there.

Does clearing Outlook cache free space permanently?
It may free space temporarily, but Outlook can recreate an OST and download the mailbox again. To manage ongoing disk use, review the offline mail range and archive or remove data only through the appropriate account or retention settings.

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