JV-MailChimp - Single Opt-In Vs Double Opt-In Method
Before you begin to build your mailing list, you'll need to decide if you want customers to use a single opt-in or a double opt-in to your email list. Of course, in order to do that, you'll also need to understand what a single email opt-in and a double opt-in.
Single Opt-in means a sign-up process in which a user does not need to confirm that he or she signed up. In short, once the user enters his or her email into the sign-up or join box, the email address is instantly added to your email list and the new subscriber instantly starts receiving emails from you.
Unlike a single email opt-in sign-up, a double email opt-in sign-up requires that a user confirm that he or she has actively joined your email list. This is typically done by generating an email to the user after he or she signs up. That email then requires the user to click a link in the email in order to confirm that he or she is the owner of the email address and does want to receive emails from you. This process eliminates many of the "bad" email addresses that get entered into a system (typos or incorrect email addresses) and also protects against instances where somebody may be taking "revenge" on another person by using their email address to sign up for numerous email marketing lists.