In Rare, you have the option to collect emails based on single or double email opt-in. Both have many advantages and disadvantages on how you build your list. You will have to decide which is best for your business. Here is a brief explanation of both:
A single sign-up process in which a user does not need to confirm their email address after they have signed up to receive marketing from you. Their email is instantly added to your mailing list, and they can start to receive emails from you right away.
Requires the user to confirm their email address once they join your mailing list. This is done by confirming through a link that is sent to their inbox. This process eliminates incorrect email addresses that may get entered into your mailing list, and ensures that the user agrees to receive marketing from you.
In order to set this in your Rare account, you can do this in the Setup Wizard (account name>Setup Wizard>#4. Configure your settings) under option 5. Subscription/unsubscribe:
By default, your Rare account is set to single opt-in, so if you would like to change it, you can select the "Double Opt-in" check box.