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Disabling Outlook restricted extensions

Sunday, March 15th, 2009

Many of us in the IT industry have battled the inevitable outlook message "Outlook has blocked potentially unsafe attachments. This arises with the default set of rules in outlook to limit security threats to incoming attachments in your email... which is very 1990s. (All GOOD checks actually test the contents of the file and check for content-types, but that is an aside).

First a disclaimer: Do not make any of these changes if it is against your IT policy, or if you are not an advanced user of Outlook and Windows in general. This requires a change in your registry and you should not do so unless you know what you are doing, and only after you have made a full registry backup. If none of that makes sense then don't proceed.

To add file extensions which you no longer want to be blocked, go to regedit (start -> run -> regedit) and navigate to: HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Security

The numerical value after Office\ may be different depending on your version of Outlook.

Under the key, select add new string value, and name it Level1Remove.

The value of Level1Remove should be a semicolon-separated list, such as:


Save the value, exit regedit, then restart Outlook and you are good to go without further restrictions on those file extensions.

Outlookin' Tom Out.


Howto Outlook

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