Is it possible for attendees of meetings to update the meeting by either
adding text or attaching files to the meeting in Outlook 2003 (on Exchange
2003) without using a meeting Workspace?

Somehow some of my users have managed to add attachments to meetings they
are the attendees (not the organizer of) and the organizer can see the
attachments. Other users are unable to do this but I want to figure out how
it was done so that everyone can do it.

Some people only have Accept, Decline, Propose new time on meetings they
have already accepted others have Save and Close and Send Update. Everyone
has the same permissions on the calendar that the meetings are setup on.

I am probably missing something glaringly obvious but any help would be
greatly appreciated.