A/B split—A method of testing in which a small, random sample of an email list is split and sent as two different emails, allowing marketers to test the effectiveness of each and determine which works best and should be sent to the rest of the list.
Above the fold—A design term referring to the top half (when discussing email) of an email. The majority of effective emails contain the most important elements above the fold, which often is viewed by more recipients.
Authentication—An automated process used by Internet service providers (ISPs) and email service providers (ESPs) to verify an email sender's identity.
Autoresponder—An email message that is automatically generated and sent to new subscribers, inquiries, unsubscribers, ...