Double opt-in refers to a sign up process in which a new subscriber fills out an online form to join a mailing list and is then sent a verification email asking them to click a link to verify their sign up. If the new subscriber does not click this verification link, then they are not added to the mailing list.
Only those people with access to the subscribing email account can respond to the confirmation message, greatly reducing the chance of abuse. For this reason, double opt-in is regarded as the gold standard for securely building an email marketing list. Our sign up form generates double opt-in forms.