What if I send my app invitation email and then add more attendees? Will this double email my attendees?

After you have sent an email to your attendees from the dashboard you will see your sent email(s) and any drafts you have saved. If you have added more attendees to your event since you sent your last email and want to send them the same information without double emailing all the rest of the attendees you can click 'Action' and 'Resend to New Attendees.' 

You can also select specific individuals to send a new email campaign if you only want to send to a select few people. To do this you would click 'Create Email Campaign' and choose the recipients 'Or select attendees manually' button.