The best contact list is one filled with recipients who’ve explicitly requested that you send them something, but there are many kinds of mailing lists used in the industry, classified according to how reliably the recipients have indicated their willingness to be contacted:

CONFIRMED/DOUBLE OPT-IN

  • Steps:
    • A subscriber either manually inputs his email or checks a a box confirming he wants to opt-in to the list.
    • A confirmation email is sent to their email address
    • The subscriber must take an action (like clicking a link) in order to confirm that the address is valid
    • A welcome email is sent.
  • Reliability: Most reliable method; default setting for new accounts.
  • Benefits:
    • Only the true owner of the email address can sign up and confirm their subscription - therefore generating very few complaints, if any.
    • It also prevents you from adding any incorrectly typed, role-based or spam trap addresses to your list as they will never complete the confirmation process.

NOTIFIED OPT-IN

  • Steps:
    • A subscriber either manually inputs his email or checks a a box confirming he wants to opt-in to the list.
    • A welcome email is sent.
  • Reliability: Second best method.
  • Benefits:
    • Opt-in method is explicit and therefore compliant with Anti-Spam legislation
  • Drawbacks:
    • Prone to abuse
    • Can lead to lists with more complaints than a two-step double opt-in process

SINGLE OPT-IN

  • Steps: A potential subscriber provides his email or checks a subscription box.
  • Reliability: Low
  • Benefits:
    • Opt-in method is explicit and therefore compliant with Anti-Spam legislation
  • Drawbacks:
    • Prone to abuse
    • Generally results in a higher spam and/or bounce rate that can lead to serious delivery problems.

OPT-OUT (IMPLIED CONSENT)

  • Steps: Email addresses are added automatically and users are required to either unsubscribe upon receipt of an email or to uncheck a box when submitting their data on a form, as part of a checkout process or during account creation.
  • Reliability: Poor
  • Drawbacks:
    • Can make recipients feel as if they were tricked, damaging your relationship, reputation and in turn your delivery in the process.
    • Typically generates a large volume of emails flagged as "SPAM" which negatively affects your Sender Reputation and in turn your delivery rates.