Issues opening Excel attachments

Clear Outlook’s Secure Temp folder

Main possible cause that Excel attachments are not opening correctly or with an error is because of other Excel files or templates in Outlook’s Secure Temp folder. 

The Secure Temp folder is the folder that Outlook uses to (temporarily) store attachments to that are being opened directly from within Outlook. Under certain conditions, this Secure Temp folder is not always cleaned correctly. 

In that case, you can clean it manually and see if the attachment is opened correctly now.

Outlook Secure Temp folder

Step 1: Locate the folder
The folder location is stored in the registry in the following key;

Outlook 97	HKEY_CURRENT_USER\Software\Microsoft\Office\8.0\Outlook\Security
Outlook 98	HKEY_CURRENT_USER\Software\Microsoft\Office\8.5\Outlook\Security
Outlook 2000	HKEY_CURRENT_USER\Software\Microsoft\Office\9.0\Outlook\Security
Outlook 2002/XP	HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Security
Outlook 2003	HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Security
Outlook 2007	HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\Security
Outlook 2010	HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Security
Outlook 2013	HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Security
Outlook 2016	HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security

Step 2: Get to the folder

1. Open the OutlookSecureTempFolder registry key from the location provided in Step 1.
2. Copy the path from the key.
3. Open Explorer.
4. Paste the address in the Address Bar and press Enter.

Paste the found path in the address bar of File Explorer to easily get to the folder.