How To Clear Cache In Outlook

Outlook’s cached data helps emails load faster, but clearing it can resolve sync errors and free up storage space. If you’ve been wondering how to clear cache in Outlook, you’re in the right place. This guide walks you through every method step by step, so you can get your email client running smoothly again.

Cached data includes temporary files, offline folders, and autocomplete entries. Over time, this data can become corrupted or bloated, causing Outlook to slow down or fail to sync. Clearing the cache is a simple fix that often solves these issues.

Why Clearing Outlook Cache Matters

Outlook stores a local copy of your mailbox to speed up loading. But when this cache gets too large or damaged, you might see errors like “Outlook is not responding” or “Cannot start Microsoft Outlook.” Clearing the cache forces Outlook to rebuild the local copy, which can fix these problems.

You might also notice that your search results are missing or that emails don’t appear correctly. These are classic signs that your cache needs a refresh. The process is safe and won’t delete your actual emails—only the temporary files.

There are several ways to clear the cache, depending on what type of cached data you want to remove. Below are the most effective methods, from simple to more advanced.

Method 1: Clear Autocomplete Cache

The autocomplete cache stores email addresses you’ve typed before. If you see old or incorrect addresses, clearing this cache helps.

Open Outlook and click on “File” in the top-left corner.
Select “Options” from the menu.
In the Outlook Options window, click on “Mail.”
Under the “Send messages” section, look for “Use Auto-Complete List.”
Click “Empty Auto-Complete List” and confirm.
Click “OK” to save changes.

This method removes only the autocomplete suggestions, not your contacts or emails. You’ll need to start typing addresses again, but Outlook will learn them over time.

Method 2: Clear Cached Exchange Mode Data

If you use Outlook with an Exchange account, the cached mode data can take up significant space. Here’s how to clear it:

Close Outlook completely.
Open the Control Panel on your computer.
Click on “Mail” (or “Mail (Microsoft Outlook 365)” depending on your version).
In the Mail Setup window, click “Show Profiles.”
Select your Outlook profile and click “Properties.”
Click on “Data Files” to see your OST file location.
Note the file path, then close the window.
Navigate to that folder in File Explorer.
Find the .ost file (it’s usually named after your email address).
Rename the file to something like “old_outlook.ost” or delete it.
Restart Outlook. It will create a new OST file and sync your mailbox.

Be patient—this process can take a while if you have a large mailbox. Your emails will reappear as they download from the server.

Method 3: Clear Temporary Files Cache

Outlook also stores temporary files in your Windows user folder. Clearing these can free up space and fix minor glitches.

Close Outlook.
Press the Windows key + R to open the Run dialog.
Type %temp% and press Enter.
This opens the Temp folder. Select all files (Ctrl + A) and delete them.
If some files are in use, skip them.
Also clear the Recycle Bin afterward.

You can also clear the Outlook-specific temp folder. In the Run dialog, type %localappdata%\Microsoft\Outlook and delete the “RoamCache” folder inside. This removes cached data for search and folder views.

Method 4: Clear Search Cache

Outlook’s search index can get corrupted, making it hard to find emails. Clearing the search cache rebuilds the index.

Close Outlook.
Go to Control Panel and click “Indexing Options.”
Click “Advanced” at the bottom.
Under “Troubleshooting,” click “Rebuild.”
Confirm the action. This may take several hours for large mailboxes.
After rebuilding, restart Outlook and let the indexing complete.

Your search results should now be accurate and fast. Note that this process uses CPU resources, so it’s best done when you’re not using your computer heavily.

Clearing Cache In Outlook For Mac

Mac users have a slightly different process. Here’s how to clear cache in Outlook for Mac:

Quit Outlook completely.
Open Finder and click “Go” in the menu bar.
Select “Go to Folder” and type ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile.
Look for a folder named “Data” or “Cache.”
Move these folders to the Trash.
Empty the Trash and restart Outlook.

Outlook for Mac will recreate these folders when it starts. Your emails will sync again from the server. This method clears most cached data, including attachments and folder lists.

When To Clear Cache In Outlook

You don’t need to clear the cache every day. Only do it when you experience specific problems:

Outlook is running very slowly.
Emails are not syncing properly.
Search results are missing or incomplete.
You see error messages about corrupted data.
You’re running low on disk space.

Clearing the cache too often can actually slow you down, because Outlook has to rebuild the local copy each time. Use it as a troubleshooting step, not a maintenance routine.

What Happens After Clearing Cache

After you clear the cache, Outlook will download a fresh copy of your mailbox from the server. This means:

Your emails will still be there, but they may take a few minutes to appear.
Offline access to older emails might be limited until the sync completes.
Any custom folder views or rules will be preserved, since those are stored separately.
Your autocomplete list will be empty if you cleared that cache.

If you’re using an Exchange account, the server holds the master copy. So clearing the local cache is safe—you won’t lose any data permanently.

Common Mistakes When Clearing Cache

People often make these errors when trying to clear the cache:

Deleting the wrong file: Make sure you’re deleting the .ost or .pst file, not your actual mailbox data.
Not closing Outlook first: If Outlook is running, some cache files are locked and can’t be deleted.
Forgetting to backup: While rare, it’s smart to backup your .pst file before deleting anything.
Skipping the temp folder: Many users only clear the autocomplete list and wonder why issues persist.

Take your time and follow each step carefully. If you’re unsure, start with the simplest method (autocomplete) and work your way up.

Advanced Cache Clearing Options

For IT professionals or advanced users, there are more powerful tools:

Using Command Line

You can clear the cache using the Outlook command line switch. Close Outlook, then press Windows + R and type:

outlook.exe /cleanviews — This resets folder views.

outlook.exe /cleanreminders — This clears reminders.

outlook.exe /cleanfreebusy — This resets free/busy information.

Using Registry Editor

Warning: Editing the registry can cause problems if done incorrectly. Backup your registry first. Navigate to:

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Search

Delete the “Search” key to clear the search cache. This is a more thorough method than the Indexing Options approach.

Frequently Asked Questions

Will Clearing Cache Delete My Emails?

No, clearing the cache only removes temporary files. Your emails are stored on the server and will be downloaded again. However, if you delete your .pst file (for POP accounts), you could lose emails that aren’t backed up. Always backup first.

How Often Should I Clear Outlook Cache?

Only when you encounter problems like slow performance or sync errors. Doing it monthly as a preventive measure is fine, but not necessary. Over-clearing can waste time on re-syncing.

Does Clearing Cache Affect Other Microsoft Apps?

No, the Outlook cache is separate from other Office apps. Clearing it won’t affect Word, Excel, or Teams. However, if you clear the Windows temp folder, it may affect other programs temporarily.

Can I Clear Cache Without Losing Autocomplete?

Yes, if you only clear the temporary files or search cache, your autocomplete list remains intact. Only the first method (clearing autocomplete) removes those suggestions. Choose the method based on what you need.

Why Is My Outlook Still Slow After Clearing Cache?

If clearing the cache doesn’t help, the issue might be a large mailbox, add-ins, or network problems. Try disabling add-ins, compacting your data file, or checking your internet connection. Sometimes a full repair installation of Office is needed.

Final Tips For A Smooth Outlook Experience

Keeping Outlook fast isn’t just about clearing the cache. Here are a few extra tips:

Archive old emails regularly to keep your mailbox size manageable.
Disable add-ins you don’t use—they can slow down startup.
Update Outlook to the latest version for bug fixes.
Use online mode if you have a fast internet connection and don’t need offline access.
Run the Inbox Repair Tool (scanpst.exe) if you suspect file corruption.

Now you know exactly how to clear cache in Outlook. Whether you’re using Windows or Mac, these methods will help you resolve common issues and keep your email client running efficiently. Try the simplest method first, and only move to advanced steps if needed. Your Outlook will thank you.