There are a few things to keep in mind:
1.) You have to set up SMTP in order to use this feature. You can do it by going to the Launch tab and then Email Broadcast:
2.) Only participants who have confirmed their emails will receive the email blast sent from Vyper. This is due to potential spam issues.
Note: if you'd like to send an email to ALL participants, you can manually export your email list and use your email service provider.