The email service is included in the plans and is completely free. This way you can avoid purchasing third party paid services.
The Metooo email invite is an effective RSVP, it can increase ticket sales, and is coordinated with the event page. A few clicks are enough to be able to compose your recipient lists and send an invite.
If you need more email invites than the number available in the Open and PRO packs, you can purchase an additional pack of invites.