Similar to What happens if I share a PreVeil Drive folder with someone who doesn't have PreVeil?, if you use PreVeil to send an email to someone who is not yet using PreVeil, your intended recipient will receive a personalized invitation asking them to join PreVeil.
The invitation email looks like this:
The recipient will need to install PreVeil on their device and create an account with the email address where they received the invitation. When the recipient accesses their PreVeil account, your encrypted message will be waiting in their inbox. You will also receive an in-PreVeil notification confirming that your invitee has created a PreVeil account.