You might want to post this on the Collaboration/Beta Testing forum. That is the appropriate place for a question like this.
If you email a forum member uninvited, they may well be hostile, and this will give a negative opinion of your product regardless of how good it is. Indeed, you may find that some of the members you want to contact have disabled email notifications.
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington