Where does Microsoft create the Outlook Temporary folder (better known as the Outlook OLK folder)? Or, where does Microsoft store that pesky OLK folder and temporary data such as attachments?
Depending on the operating system, version of Outlook, and the user currently logged in, the OLK temporary folder gets created in a different location. The good news is, it’s simple to find no matter the version of Outlook, including Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019, and Outlook for Microsoft 365 (or O365).
To determine the spots where folders got created, open the Windows registry using regedit.exe and look for the Registry key OutlookSecureTempFolder using the map below:
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 Outlook 2019 & O365: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security
Using the chart above, here are a few screenshots comparing my Windows XP system running Office 2003 vs. my Windows 8.1 system running Office 2010. And here is my current desktop, Windows 10, and Outlook for Microsoft 365.
As you can see from the screenshot, the OLK temporary folder is located at:
Background – What is the OLK folder, and why is it so hard to find?
When you open file attachments from an email, Outlook needs to save the files somewhere on your hard drive before opening the file. To do this, it checks the registry to see if Outlook has already created a temporary folder (aka – the outlook OLK folder) for this use. If Outlook finds a registry entry for the OLK folder, it saves the file and opens it for you. However, if the registry entry doesn’t exist, it creates, it then saves a copy of the attachment in the folder.
For example, let’s say your running Windows 10 and Outlook for Microsoft 365 like me. When you open your first attachment in Outlook, your computer will create the following sub-folder to store that attachment temporarily:
In this example, the logged-in user’s name would replace the user-name, and the subfolder at the end will be created with a randomly generated sequence of letters and numbers.
This information can be very useful. For example, let’s say you open an attachment, make a bunch of changes then close it before you have a chance to save it. Or, perhaps your PC crashes before you can save it. The good news is you can probably find the file in the Outlook Temporary OLK folder and recover your work. Speaking of recovering your data, have you configured the Word and Excel autosave feature?
Now the bad news
Let’s say you open an attachment that contains sensitive or confidential information. While reading the document, Outlook unexpectedly closes. In this scenario, the attachment will remain in the Outlook Temporary folder indefinitely since Outlook normally deletes them when you close the document correctly. Now let’s say your PC is lost or stolen. Yup, all your documents are just waiting for the new owner of your PC to find and open them.
Don’t think this is very common? Just look. No really. Stop reading and look in your OLK folder. If you’ve been using your computer for any length of time, you will likely find a few dozen files sitting there.
Protect yourself against the OLK folder
Each time I build a new machine, one of the first things I do is encrypt the OLK folder using the built-in Microsoft file and folder encryption called EFS. It’s fast, easy, and adds a nice security layer should I lose my laptop and haven’t had a chance to encrypt my hard drive. Now, if you’re using a home PC and don’t have IT guys managing your system, you’re probably okay with just Wiping your system if you sell it or swap out your hard drive for a faster SSD drive.