If you have sent out an email to registered attendees and new ones are added, you can resend the email so that it goes out only to those who registered for the event after the message was sent.
Resend an email to new attendees
To resend a message to new attendees follow these steps:
Click on `Messages`
Select the message you want to resend under the title `Sent`
Click on the button `Send to new recipients`.
The message will only be sent to the attendees who have not yet received it.