How to clear temp in Outlook?

To effectively clear temporary files in Outlook, you'll need to address both Outlook-specific caches and general system-wide temporary folders that can impact its performance and stability. This process helps free up disk space, resolve potential glitches, and improve overall responsiveness.

Why Clear Temporary Files in Outlook?

Over time, Outlook and your operating system accumulate various temporary files, cache data, and prefetch files. These files are typically created to speed up operations or store temporary data. However, an excessive buildup can lead to:

Slower performance: Outlook might open or operate sluggishly.
Disk space consumption: Unnecessary files can consume significant storage.
Application errors: Corrupted temporary files can cause Outlook to crash or malfunction.
Privacy concerns: Cached data, such as attachment copies, might linger longer than desired.

Methods to Clear Temporary Files Affecting Outlook

Clearing temporary files involves several steps, covering both system-level and Outlook-specific locations.

1. Clearing General System Temporary Files

Outlook, like other applications, relies on system-wide temporary folders. Clearing these can contribute significantly to a smoother experience.

Cleanup %TEMP% Folder

This folder stores temporary files created by various applications, including those that Outlook might generate or interact with.

Step 1: Open the Run dialog.
Simultaneously press the Windows key + R hotkeys on your keyboard.
Step 2: Access the %TEMP% folder.
In the Run dialog box, type %TEMP% and click OK.
Step 3: Delete contents.
The %TEMP% folder will open. Select all files and folders within it (you can press Ctrl + A) and permanently delete them (e.g., by pressing Shift + Delete or dragging them to the Recycle Bin and emptying it).
It is normal if some files or folders cannot be deleted; this usually means they are currently in use by an active program.

Cleanup PREFETCH Folder

The PREFETCH folder stores prefetch files, which Windows uses to speed up the launch of frequently used applications. While the reference only instructs to open this folder, users often clear its contents during a thorough system cleanup.

Step 1: Open the Run dialog.
Simultaneously press the Windows key + R hotkeys on your keyboard.
Step 2: Access the PREFETCH folder.
In the Run dialog box, type PREFETCH and click OK.
Step 3: (Optional) Delete contents.
The PREFETCH folder will open. If prompted for administrator permissions, click Continue. While deleting these files is generally safe, it might temporarily slow down the launch of your applications as Windows rebuilds the prefetch data. You can select and delete its contents if you wish to perform a comprehensive cleanup.

2. Deleting Outlook's SecureTemp Folder Contents

Outlook has a hidden "SecureTemp" folder where it temporarily saves attachments when you open them. This folder often retains old copies, consuming space and potentially posing security risks if not cleared.

Step 1: Locate the SecureTemp Folder Path.
The exact path varies depending on your Outlook version and operating system. The easiest way to find it is to open an attachment from an email in Outlook, then go to File > Info > Open File Location (if available), or check the file properties to see its current temporary path.
Alternatively, you can find the path in the Windows Registry:
1. Press Windows key + R, type regedit, and press Enter.
2. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\<version>\Outlook\Security (replace <version> with your Outlook version, e.g., 16.0 for Outlook 2016, 2019, 2021, and Microsoft 365).
3. Look for a string value named OutlookSecureTempFolder. Its data will show the path.
Step 2: Close Outlook.
Ensure Outlook is completely closed before proceeding.
Step 3: Navigate to the folder and delete contents.
Paste the identified path into the Windows Explorer address bar and press Enter. Select all files and folders within this OutlookSecureTempFolder and delete them.

3. Managing Outlook Cache and Data Files

Beyond temporary files, Outlook maintains various caches and data files that can grow large and impact performance.

Clear AutoComplete List (Suggested Contacts)

Outlook keeps a cache of email addresses you've previously sent messages to. If this list becomes corrupted or too large, it can cause issues.

Step 1: Open Outlook.
Step 2: Go to File > Options.
Step 3: Select Mail.
Step 4: Scroll down to "Send messages" section.
Step 5: Click "Empty Auto-Complete List".

Compact Outlook Data Files (.PST/.OST)

Outlook stores your mail, calendar, and contacts in either Personal Storage Table (.pst) files (for POP accounts) or Offline Storage Table (.ost) files (for Exchange, Outlook.com, and IMAP accounts). Compacting these files reduces their size by removing empty space left by deleted items.

Step 1: Open Outlook.
Step 2: Go to File > Account Settings > Account Settings.
Step 3: Select the "Data Files" tab.
Step 4: Select the .pst or .ost file you want to compact and click "Settings".
Step 5: Click "Advanced" then "Outlook Data File Settings".
Step 6: Click "Compact Now".
Note: For .ost files, sometimes the most effective way to clear a corrupted cache is to close Outlook, delete the .ost file, and let Outlook rebuild it from the server when you restart it. Ensure you have a stable internet connection before doing this.

Empty Deleted Items Folder

This is a simple but effective step to reduce the size of your Outlook data files.

Step 1: In Outlook, right-click the "Deleted Items" folder.
Step 2: Select "Empty Folder".
Step 3: Confirm the deletion.

Summary of Temporary File Locations and Actions

Location	Type of Files Stored	Action	Impact
`%TEMP%`	General system temporary files	Delete all contents (skip files in use).	Frees disk space, improves general system performance.
`PREFETCH`	Application launch optimization files	(Optional) Delete contents; might temporarily slow application launch.	Can free minor space; less direct performance gain than `%TEMP%`.
Outlook SecureTemp Folder	Temporary attachment copies	Close Outlook, navigate to folder path (via Registry/attachment open), delete all contents.	Frees disk space, improves security/privacy of attachments.
Outlook AutoComplete List	Cached email addresses	Empty via Outlook Options.	Resolves issues with corrupted contact suggestions.
`.PST` / `.OST` Data Files	Outlook mail, calendar, contacts	Compact files via Account Settings > Data Files.	Reduces file size, improves performance, especially for large mailboxes.
Deleted Items Folder (within Outlook)	Deleted emails, items	Right-click and "Empty Folder".	Frees up space within your Outlook data file.

By systematically clearing these temporary and cached files, you can ensure a cleaner, faster, and more reliable Outlook experience.