Some file extensions are blocked by Microsoft Outlook for the potential damage that they may cause. File types blocked include EXE, COM, MDB and many others.
Outlook displays a message that it has blocked the attachment:
- On the desktop running Outlook, open Registry Editor.
- Navigate to HKEY_CURRENT_USERSoftwareMicrosoftOfficexx.x OutlookSecurity where xx.x is your Outlook version number (9.0, 10.0, or 11.0)
- Add a new string named Level1Remove
- Add value to this string with all the extensions that you want to unblock, separated by a semicolon. (For example: .mdb;.url ) Remember to put the dot before the extension.
It should, however, be kept in mind that unblocking a particular file type introduces new risk, as the user can also receive a malicious file of the same type from another user or the internet and he/she might inadvertently open it.
For Outlook 2007, you need to insert the string in the following key HKEY_CURRENT_USERSoftwarePoliciesMicrosoftOffice12.0OutlookSecurity. If the key path doesn’t exist, you can create it.