I got a call from a Client today about attachments blocked on Outlook 2007. This was bugging them, since they could not figure out how to correct it. So I remote into the machine, and even I was having trouble with getting it to allow a pst file to be downloaded.
Issue was not easily solved in the Outlook interface. The issue had to be reg hacked to allow pst files to be downloaded.
HKEY_CURRENT_USER\Software\Microsoft\Office\XX.X\Outlook\Security\
So this is the area you need to look at in the Registry.
XX.X is related to the version of outlook you are using.
You need to add a new String called Level1Remove
and for the value you need to put in the file type you want to unblock.
Very important you only make the changes you need. For this example,
it was .pst for the file in question.