Unable to attach a file or open an attached file in Microsoft Outlook
This is mainly because the user might not have the right permission to the temp folder.
One solution is to create a new temp folder for them and give them permission to write and read to it. E.g. c:\temp
You will need to edit the registry too. You can do this by typing ‘regedit’ on the ‘run’ menu.
Look inside the ‘HKEY_Current_User\Software\Microsoft\Office\Version\outlook\security\’ for the outlookSecureTempFolder key. You can also do a find for the ‘outlookSecureTempFolder’ key too. Once you found this key, change the path to the new temp folder that you created.