Email Marketing Glossary
Email marketing terms defined in plain English, with what they change in practice.
The three that decide everything
- SPF, DKIM, DMARCThree checks, six lines to add to your DNS. Without them, Gmail and Yahoo have been refusing bulk sends since February 2024 — before they even look at what you wrote.
- Double opt-inConfirmation by click. It is what separates a list that follows you from a list that generates complaints.
- BouncePermanent or temporary, it is not the same problem: the first removes the address from your list, the second does not touch it.
All 10 terms, in order
Click-through rate (CTR)The share of recipients who clicked on at least one link in your email, measured against messages delivered. Unlike open rate, it is not affected by Apple MPP.Double opt-inA signup confirmed by clicking a confirmation link in a verification email sent to the address entered, before any campaign is sent.Email bounceAn email rejected by the recipient's server. Permanent when the address does not exist; temporary when the mailbox is full or the server is unavailable.Email open rateThe share of recipients who opened your email, measured against messages successfully delivered. Inflated since Apple Mail Privacy Protection launched in 2021.Email preheaderThe line of text displayed just after the subject line in the inbox preview, before the message is opened by the recipient.Opt-in and opt-outTwo opposite ways of building a list: opt-in writes only to those who said yes, opt-out writes to everyone who has not said no.SegmentationSetting a condition on your list to isolate a targeted subset of subscribers, and knowing how many people that condition currently represents.SPF, DKIM and DMARCThree DNS-based checks that email providers run on your domain to verify that mail genuinely comes from you and has not been tampered with.Suppression listThe list of addresses you must never email again: unsubscribers, hard bounces, and recipients who marked your message as spam. It fills automatically.Transactional emailAn email your application sends to one person because of something they did: a purchase, a password request, a new account.
These terms make more sense once you use them
Double opt-in and bounce handling are built in — not options to enable. For domain authentication, the Domains screen gives you the six exact records to publish with your hosting provider, noting which ones are required before you can send.