coordination with Lotus Notes Calendar events

Upon switching from Outlook 2003 to 2007 versions, my meeting invitations
that I receive from external Lotus Notes users do not automatically process
through to the calendar. They come in as email with an attachment that I
have to open which then processes through to the calendar for acceptance,
etc. Is there a tool that I can add in to Outlook so that these will
automatically process through or is that something that Lotus Notes needs to
do in order to allow calendar events to work well with Outlook 2007