I have a user (UserA) who is trying to share a non-default contact list. When attempting to send it to a specific user (UserB), the error "Error while preparing to send sharing message." appears (both with, and without the Editor checkbox)
This is not so when attempting to send it to myself. Neither myself or UserB have any rights to any folders of UserA's.
Exhange 2007 on Server 2003, Outlook 2010.