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Glossary

Quick definitions for terms you’ll see across this library.

  • Amazon SES — Amazon Simple Email Service — a cloud email-sending API often used for transactional mail and self-hosted ESPs.
  • BIMI — Brand Indicators for Message Identification — a standard that can display a brand logo in supporting inboxes when DMARC is enforced.
  • CTR — Click-Through Rate — the percentage of email recipients who clicked one or more links in a message.
  • Deliverability — The ability for legitimate email to reach the inbox rather than spam or promotions folders.
  • DKIM — DomainKeys Identified Mail — a cryptographic signature that proves an email was authorized by the sending domain.
  • DMARC — Domain-based Message Authentication, Reporting, and Conformance — a policy that tells receivers how to handle SPF/DKIM failures and where to send reports.
  • Double Opt-In — A subscription process where a user confirms their email address before being added to a mailing list.
  • ESP — Email Service Provider — a platform used to send, manage, and measure marketing or transactional email campaigns.
  • Lead Magnet — A free resource (ebook, checklist, template) offered in exchange for an email address.
  • Lifecycle Email — Automated messages tied to a customer journey stage such as welcome, onboarding, win-back, or renewal.
  • List Hygiene — Ongoing cleanup of invalid, inactive, or risky addresses to protect sender reputation and improve engagement.
  • MJML — A markup language and framework for building responsive HTML emails with a simplified component syntax.
  • Open Rate — The percentage of delivered emails that were opened. Increasingly noisy due to Apple Mail Privacy Protection and similar features.
  • Personalization — Adapting content, offers, or send timing to an individual recipient using known data and behavior.
  • Seed List — A set of test inboxes across providers used to monitor placement, rendering, and deliverability.
  • Segmentation — Splitting an audience into groups based on behavior, attributes, or preferences so messaging can be more relevant.
  • Single Opt-In — A subscription process that adds an address immediately after form submission without a confirmation email.
  • SPF — Sender Policy Framework — a DNS record that lists which servers are allowed to send email for a domain.
  • Transactional Email — Message triggered by a user action — password resets, receipts, shipping updates — rather than a marketing broadcast.
  • Warm-up — Gradually increasing send volume from a new domain or IP so mailbox providers learn to trust the sender.

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