Email Marketing Glossary

A series of emails sent automatically based on subscriber behavior or time triggers.

A privacy feature that pre-fetches every email image, making open rates unreliable for Apple Mail users.

Sending two variants of an email to small samples to find the winner before sending to the full list.

The percentage of sent emails that were not delivered for any reason.

The percentage of delivered emails where the recipient clicked at least one link.

Of the people who opened, the percentage who also clicked.

US law requiring marketing emails to include a physical address and a working unsubscribe link.

The percentage of recipients who took the desired action (purchase, signup, download).

A cryptographic signature added to outgoing emails that proves the message really came from your domain and was not tampered with.

A policy you publish in DNS that tells inbox providers what to do if SPF or DKIM checks fail.

A signup method that requires a subscriber to click a confirmation link in an email before they are added to your list.

The ability to consistently land in the inbox rather than the spam folder or being rejected.

A platform that lets you send marketing email at scale — Mailchimp, Kit, ActiveCampaign, Klaviyo, etc.

European data protection law that requires explicit consent before sending marketing email to EU residents.

A permanent delivery failure — the address does not exist or the domain is invalid.

Gradually increasing send volume on a new IP or domain to build sender reputation.

The ongoing practice of removing invalid, inactive, and risky addresses from your email list.

The natural rate at which an email list goes stale — typically 2–3% per month.

A free piece of value (PDF, template, mini-course, tool) offered in exchange for an email signup.

The percentage of delivered emails that were opened by the recipient.

The line of text that appears next to or beneath the subject line in the inbox preview.

A DNS record that lists which servers are allowed to send email on behalf of your domain.

A temporary delivery failure — the inbox is full, the server is down, or the message is too large.

An email address used by inbox providers and blocklists to identify careless senders.

A score inbox providers assign to your sending domain and IP based on engagement, complaints, and bounces.

Dividing your email list into smaller groups based on behavior, demographics, or interests.

The percentage of recipients who clicked "report spam" instead of unsubscribing.

A label attached to a subscriber that describes their behavior, interests, or attributes.

A one-off email triggered by a specific user action — receipts, password resets, shipping notifications.

The percentage of recipients who unsubscribe from a given campaign.