To send an email only to those who have replied that they are attending your event, follow these steps:
Click on `Messages` in the menu
Click on `Email & SMS`
Click on `Compose`
Click on the tab `Content`
Write the text with information for your participants by filling the fields under Subject (headline) and Message (text)
Click on the tab `Recipients`
Check the box `Status`
Check the box `Attending` to choose to send the message only to those that have responded that they will attend your event.