An additional solution for Outlook 2010:
Standard warnings apply for registry modifications.
After you have made a backup of the registry, try the registry key as follows:
1. Exit Outlook 2010.
2. Start Registry Editor.
3. Locate and then select the following registry subkeys:
HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Preferences
3. On the Edit menu, point to New, and then click DWORD Value.
5. Type DisableTNEF, and then press ENTER.
6. Right-click DisableTNEF, and then click Modify.
7. In the Value data box, type 1, and then click OK.
8. Exit Registry Editor.
9. Restart the computer.