Understanding single and confirmed opt-in

When you create a new subscriber list you are required to choose a list type; either single opt-in or confirmed opt-in.

This page explains how both list types work, and offers advice to help you decide which one is best for you.

Single opt-in versus confirmed opt-in

The type of list that is right for you, or your client, depends on the quality of the list you require as well as the quantity of subscribers you are hoping to attract. The pros and cons are explained below.

Note: The descriptions below, for how each list type works, also apply to subscribers who are added to a list in your account via our API.

Single opt-in lists

This list type simply requires someone to sign up through a subscribe form and submit their details. They are immediately added to the subscriber list the form points to.

Advantages:
  • Will grow your list faster because a one-step sign up process equals higher subscribe rates.
Disadvantages:
  • Opens your subscriber list to collecting invalid, faulty and non-consenting email addresses, resulting from:
    • Email addresses being added to the list by spambots.
    • Errors made when entering emails, for example a typo that results in someone submitting an address that is not theirs.
    • Legitimate addresses being added by someone who does not own the address.
  • List quality is diminished, for the reasons mentioned above, making it difficult to value metrics such as open rates and engagement levels.
  • The risk of spam complaints is increased because you don't know if everyone on the list opted-in. High spam complaints and bounces, combined with low open rates and clicks, can negatively impact your delivery rates.

Confirmed opt-in lists

This list type is also known as double opt-in. When someone signs up through a subscribe form an email is immediately sent to the address they provided. (Verification emails are sent free of charge.)

The email contains a verification link which the recipient must click to confirm that they own the address. When the link is clicked, the person's email address is added to the subscriber list.

Important: The verification email is not sent if you add subscribers via file import or manual entry through your account because you will likely be adding people who have already opted in through another system. However, any subscriber added via the API to a confirmed opt-in list will be sent the verification email. 

Advantages:
  • The double opt-in process ensures people are entering their information correctly, which equals a cleaner list and lowers bounce rates.
  • Reduces the probability of spam complaints because subscribers have had to take the extra step to confirm their consent.
  • If spam complaints are recorded, you have a record of everyone's opt-in confirmation.
  • Subscribers who 'say yes twice' are generally more responsive, meaning they're more likely to open emails and click links. Positive response like this boosts your sender reputation, improving delivery rates.
Disadvantages:
  • Typically, up to 20% of initial subscribers will not complete the final confirmation step. Reasons include: people forgetting they subscribed and confirmation emails being deleted accidentally, or getting stuck in spam filters.
  • Potential subscribers who genuinely do want your newsletter may not understand the confirmation process and fail to click the link.

Unconfirmed subscribers

If the verification link in a confirmation email is not clicked, the email address is recorded with your list in the "Unconfirmed" state, as shown here:

Email addresses on the unconfirmed list will not be sent any emails, and they are not counted toward your list size for billing purposes. 

If someone on the unconfirmed list signs up the same subscriber list sometime later, they will be sent another verification email.