Get a Free Consultation

Email Marketing Glossary

Email marketing is sending targeted messages to people who have chosen to hear from you. This glossary explains more than 85 email marketing terms from A to Z in plain language, each tagged Beginner, Intermediate or Advanced, from open rate and segmentation to deliverability, SPF, DKIM and DMARC.

Updated Covers deliverability and automation Free to use, no sign-up

Email marketing terms from A to Z

ATerms starting with A

A/B Testing (Email)
Sending two versions of an email, such as different subject lines or send times, to a small sample to see which performs better, then sending the winner to the rest of the list.
Abandoned Cart Email
An automated email sent to a shopper who added items to a cart but did not buy, reminding them and nudging them to finish the purchase.
Above the Fold (Email)
The part of an email visible in the preview pane or before scrolling, the best place for the key message and main call to action.
Apple Mail Privacy Protection (MPP)
An Apple Mail feature that preloads email images, so many opens are recorded whether or not a person read the message. It inflates open rates and makes them less reliable.
Autoresponder
An automated email triggered by a specific action, such as a welcome message sent right after someone subscribes.
Automation Workflow
A sequence of emails triggered and sent automatically by subscriber behavior or timing, so each message does not need to be sent by hand.

BTerms starting with B

BIMI (Brand Indicators for Message Identification)
A standard that lets a verified brand logo appear next to its emails in supporting inboxes. It requires strong email authentication, including an enforced DMARC policy.
Blacklist (Blocklist)
A list of IP addresses or domains flagged as sources of spam. Being listed can stop emails reaching the inbox.
Bounce Rate
The percentage of sent emails that were not delivered to the recipient’s mail server, calculated as bounced emails divided by emails sent.
Broadcast Email
A single email sent to a whole list or segment at once, as opposed to an automated, triggered message.
Bulk Email
A large volume of email sent to many recipients at once, usually through an email service provider rather than a personal inbox.

CTerms starting with C

CAN-SPAM Act
A U.S. law that sets rules for commercial email, including honest subject lines, a physical postal address and a working opt-out, which must be honored within 10 business days.
Click Map (Heat Map)
A visual report that shows where recipients clicked inside an email, used to see which content and links performed best.
Click-Through Rate (CTR)
The percentage of recipients who clicked at least one link, calculated as unique clicks divided by emails delivered.
Click-to-Open Rate (CTOR)
The percentage of people who opened an email and then clicked, calculated as unique clicks divided by unique opens. It shows how compelling the content is.
Conversion Rate (Email)
The percentage of recipients who completed a desired action, such as a purchase, after clicking through from the email.
Custom Field
A piece of subscriber data, such as first name or purchase history, stored in an email platform and used to personalize messages.

DTerms starting with D

Dedicated IP
An IP address used by only one sender, which gives that sender full control over its own sending reputation.
Deliverability
The overall ability of an email to reach a recipient’s inbox, rather than being blocked, filtered or sent to spam.
DKIM (DomainKeys Identified Mail)
An email authentication method that adds a digital signature to outgoing messages, so receiving servers can verify they were not altered in transit.
DMARC
An email authentication policy that tells receiving servers what to do with messages that fail SPF or DKIM checks, which helps stop spoofing. Large senders must publish one for Gmail and Yahoo.
Domain Authentication
Verifying a sending domain’s identity through DNS records, a key factor in inbox placement and sender trust.
Double Opt-In
A signup process where a new subscriber must confirm their address by clicking a link in a follow-up email before being added to the list.
Drip Campaign
A pre-scheduled series of emails sent automatically over time to nurture a subscriber, typically triggered by signup or a specific action.

ETerms starting with E

Email Client
The app or service, such as Gmail, Outlook or Apple Mail, that a recipient uses to read email. It can affect how a message looks.
Email Authentication
The group of methods, mainly SPF, DKIM and DMARC, that prove an email really comes from the domain it claims, which protects recipients and your reputation.
Email Service Provider (ESP)
A platform, such as Mailchimp or Klaviyo, used to design, send and track email campaigns at scale.
Engagement Rate
A combined measure of how recipients interact with an email, usually counting clicks and other actions, and often opens too.
Envelope From
The technical sender address mail servers use to route and authenticate an email. It can differ from the visible “From” name.

FTerms starting with F

Frequency Cap
A limit on how many emails a subscriber receives in a set period, used to avoid overwhelming or tiring a list.
From Name
The sender name shown to recipients in their inbox, usually a brand or a person’s name rather than a raw email address.

GTerms starting with G

GDPR
The European Union’s General Data Protection Regulation, which requires a lawful basis, usually clear consent, to email people in the EU. India’s Digital Personal Data Protection Act also sets consent rules for personal data.
Gmail Promotions Tab
A separate inbox category in Gmail that automatically sorts marketing and promotional emails away from the primary inbox.
Greylisting
A spam-prevention technique where a receiving server temporarily rejects email from an unfamiliar sender and accepts it only on a repeat delivery attempt.

HTerms starting with H

Hard Bounce
A permanent delivery failure, such as sending to an address that does not exist. The address should be removed from future sends.
Header (Email Header)
The hidden technical metadata attached to an email, including routing details and authentication results, which you can see by viewing the message source.
HTML Email
An email built with design elements such as images, colors and layout, as opposed to plain, unformatted text.

ITerms starting with I

Inbox Placement Rate
The percentage of sent emails that land in the main inbox, as opposed to the spam or promotions folder.
Interest-Based Segmentation
Dividing a list by subscribers’ stated interests or past behavior, so you can send more relevant content.
IP Reputation
A score of how trustworthy a sending IP address is, based on its sending history. It influences whether emails reach the inbox.

JTerms starting with J

Junk Folder
A folder where an email client automatically puts messages it suspects are spam, separate from the main inbox.

KTerms starting with K

Key Performance Indicator (Email KPI)
A specific, measurable metric, such as click-through rate or conversion rate, used to judge whether an email program is meeting its goals.

LTerms starting with L

Lead Nurturing
A sequence of targeted emails that builds a relationship with a prospect over time and guides them toward a purchase decision.
Lifecycle Email
An email triggered by a subscriber’s stage in their relationship with a brand, such as a welcome, re-engagement or win-back message.
List Cleaning (List Hygiene)
The ongoing practice of removing invalid, inactive or unengaged addresses from an email list to protect deliverability.
List Segmentation
Dividing an email list into smaller groups based on shared characteristics, so messaging is more relevant to each group.

MTerms starting with M

Mailing List
A collection of email addresses belonging to people who have agreed to receive communications from a sender.
Marketing Automation Platform
Software that manages and triggers email, and often other, marketing messages automatically from rules and subscriber behavior.
Merge Tag (Personalization Tag)
A placeholder in an email template that is replaced with a subscriber’s own data, such as their first name, when the email is sent.
MX Record
A DNS record that says which mail servers receive email on behalf of a domain.

NTerms starting with N

Newsletter (Email Newsletter)
A regularly scheduled email that delivers curated content, updates or insights directly to subscribers.

OTerms starting with O

One-Click Unsubscribe
A way for recipients to leave a list with a single click, using the List-Unsubscribe header as well as the link in the email. Gmail and Yahoo require it from bulk senders.
Onboarding Email Series
A sequence of automated emails sent to new subscribers or customers to introduce them to a product or brand step by step.
Open Rate
The percentage of delivered emails that were opened. It is widely used but increasingly unreliable, because privacy features such as Apple Mail Privacy Protection record opens that a person never made.
Opt-In
A subscriber’s explicit consent to receive email from a sender.
Opt-Out
A subscriber’s action to stop receiving further email, usually through an unsubscribe link.

PTerms starting with P

Permission Marketing
A philosophy of communicating only with people who have clearly agreed to hear from you, rather than sending unsolicited messages.
Personalization
Tailoring email content, subject lines or offers to an individual subscriber, based on their data or behavior.
Plain-Text Email
An email in simple, unstyled text with no images or design, often used for a more personal, less salesy feel.
Postmaster Tools
Free dashboards from major mailbox providers, such as Google Postmaster Tools, that show senders their domain reputation and delivery performance.
Preheader Text
The short summary that shows next to or under the subject line in an inbox preview, used to encourage opens.

QTerms starting with Q

Quiet Hours
A set time window during which automated emails are held back, so they do not reach subscribers at inconvenient times.

RTerms starting with R

Re-Engagement Campaign
A targeted email sequence that aims to win back subscribers who have not opened or clicked recent emails.
Responsive Email Design
Email templates built to adjust their layout automatically for desktop, mobile and tablet screens.
RFM Segmentation
Segmenting subscribers by the Recency, Frequency and Monetary value of their purchases, to prioritize the most valuable customers.

STerms starting with S

Segmentation
See List Segmentation.
Send Time Optimization
Delivering an email to each subscriber at the time they are statistically most likely to engage, rather than one fixed time for everyone.
Sender Reputation
The trust mailbox providers place in a sender, based on its domain and IP history, complaint rates, bounces and engagement. It strongly affects inbox placement.
Soft Bounce
A temporary delivery failure, such as a full inbox, after which the email platform usually tries again.
Spam Complaint Rate
The percentage of delivered emails that recipients mark as spam. Gmail and Yahoo expect large senders to keep it below 0.3%, and well under 0.1% is the safer target.
Spam Score
A calculated likelihood that an email will be flagged as spam, based on factors such as content, links and sender reputation.
Spam Trap
An email address that does not belong to a real person, used by mailbox providers to spot senders with poor list hygiene.
SPF (Sender Policy Framework)
An email authentication method that lists which mail servers are allowed to send email on behalf of a domain.
Subject Line
The short line of text recipients see in their inbox before opening, a major factor in whether an email gets opened.
Subscriber
A person who has opted in to receive email from a sender.
Suppression List
A list of addresses deliberately excluded from future sends, such as unsubscribes, hard bounces and spam complaints.

TTerms starting with T

Throttling (Send Throttling)
Deliberately slowing how fast emails are sent to a mailbox provider, often when warming up a new sending domain or IP.
Transactional Email
An email triggered by a specific user action, such as an order confirmation or password reset, as opposed to a promotional message.
Trigger Email
An automated email sent in response to a specific subscriber action or event, such as an abandoned cart.

UTerms starting with U

Unengaged Subscriber
A subscriber who has not opened or clicked an email for a long time, usually a candidate for re-engagement or removal.
Unsubscribe Rate
The percentage of recipients who opted out of future emails after a specific send.

VTerms starting with V

Validation (Email Validation)
Checking email addresses for correct format and deliverability before adding them to a list, to reduce bounces.
Variable Content (Dynamic Content)
Email content that changes automatically for each recipient based on their data or behavior, beyond simple name personalization.

WTerms starting with W

Warm-Up (IP Warm-Up)
Gradually increasing the sending volume from a new IP address or domain to build a good sending reputation over time.
Welcome Email
The first automated email a new subscriber gets after signing up, usually introducing the brand and setting expectations.
Whitelist (Allowlist)
A list of trusted senders that a mailbox provider or recipient has approved to bypass spam filtering.

XTerms starting with X

X-Mailer
A technical email header field that names the software or platform used to send a message, visible when you inspect the email’s source.

YTerms starting with Y

Year-in-Review Email
An annual recap campaign that summarizes a subscriber’s activity or a brand’s milestones, popular around year-end.

ZTerms starting with Z

Zero Bounce Rate (Goal)
The aim of keeping a list so clean and validated that almost no emails fail to deliver. In practice, a very low bounce rate protects sender reputation.

What is email marketing, and how do you use this glossary?

Email marketing is the practice of sending commercial and relationship-building emails to people who have agreed to receive them, in order to inform, nurture and convert them. It is a channel you own, so it does not depend on a platform’s algorithm.

Start with the Beginner terms, such as subject line, open rate, click-through rate, list segmentation and welcome email. Move to Intermediate terms as you build automations, and use the Advanced terms for deliverability and authentication.

Search by term or filter by level above. Related terms link to each other, so you can follow an idea from one concept to the next.

Core email formulas

  • Open rateUnique opens ÷ emails delivered
  • CTRUnique clicks ÷ emails delivered
  • CTORUnique clicks ÷ unique opens
  • Bounce rateBounced emails ÷ emails sent
  • Complaint rateSpam complaints ÷ emails delivered

What do SPF, DKIM and DMARC do?

These three DNS-based checks prove your emails are genuine. Together they protect your domain and help your messages reach the inbox.

Your email platform’s setup guide shows the exact DNS records to publish.
ProtocolWhat it provesHow it works
SPFThe sending server is allowed to send for your domainA DNS record lists authorized mail servers
DKIMThe message is genuine and was not changed in transitA digital signature is added, and checked against a public key in DNS
DMARCWhat to do when SPF or DKIM fail, and who gets reportsA DNS policy: none, quarantine or reject

Since 2024, Gmail and Yahoo have required bulk senders to authenticate with SPF and DKIM, publish a DMARC policy, offer one-click unsubscribe and keep spam complaints low. Check each provider’s current rules, because requirements keep tightening.

Email marketing questions, answered

Quick answers to the most searched email marketing basics.

What is email marketing?

Email marketing is sending targeted emails to people who have agreed to receive them, in order to inform, nurture and convert them. It covers newsletters, promotions, automated sequences such as welcome emails, and transactional messages like order confirmations.

What is a good email open rate?

Benchmarks vary widely by industry and list, so compare against your own history rather than a universal number. Apple Mail Privacy Protection records many opens that people never made, so also track click-through rate, click-to-open rate and conversions.

What is the difference between a hard bounce and a soft bounce?

A hard bounce is a permanent failure, such as an address that does not exist, and should be removed from your list straight away. A soft bounce is temporary, such as a full inbox, and the platform usually retries delivery.

What are SPF, DKIM and DMARC?

They are email authentication methods. SPF lists the servers allowed to send for your domain, DKIM adds a signature that proves a message was not changed, and DMARC sets the policy for messages that fail those checks. Gmail and Yahoo require them from bulk senders.

Why do my emails go to spam?

Common causes are missing authentication, a poor sender reputation, a stale or purchased list, high complaint rates, spammy wording or a sudden jump in volume. Authenticate your domain, clean your list, send only to opted-in people and make unsubscribing easy.

What is double opt-in, and should I use it?

Double opt-in asks new subscribers to confirm their address through a link in a follow-up email. It gives a cleaner, more engaged list with fewer fake addresses and spam traps, though a few real subscribers will not confirm. Many marketers consider the trade worthwhile.

How often should I send marketing emails?

There is no universal answer. Set expectations at signup and keep to them. Watch unsubscribe and complaint rates, and use segmentation and frequency caps so engaged subscribers hear from you more often than people who have gone quiet.

What is list segmentation?

List segmentation divides your subscribers into groups by shared traits, such as interests, location, purchase history or engagement. It lets you send more relevant emails, which usually improves clicks and conversions and lowers unsubscribes.

What is the difference between transactional and marketing email?

Transactional emails are triggered by a person’s own action, such as an order confirmation or password reset. Marketing emails promote or nurture and need the recipient’s consent. Many laws treat them differently, so keep promotional content out of transactional messages.

Is this email marketing glossary free?

Yes. It is completely free to read, with no sign-up. You can search it, filter it by level and jump to any letter.

Explore our other glossaries

Looking for SEO, PPC, social media or content terms? Each has its own dedicated glossary.

Browse all glossariesThe full hub of 12 glossaries and 1,000+ terms. SEO GlossarySEO terms from on-page to technical SEO. PPC and Google AdsBidding, targeting and campaign terms. Social Media GlossaryInstagram, TikTok and paid social terms. Performance MarketingAttribution, growth and cross-channel terms. Content MarketingEditorial, writing and content strategy terms. AEO and GEO (AI Search)AI search, LLM and generative engine terms. Web Design and DevelopmentDesign, front-end, back-end and CMS terms. Analytics and ReportingGA4, statistics and dashboarding terms. E-Commerce MarketingCheckout, fulfillment and retention terms. Branding and IdentityBrand strategy, visual identity and positioning. Marketing AutomationWorkflow, CRM integration and orchestration.

Put the terms to work: take the Performance Marketing Quiz or play Find the Marketing Words.

Did not find the term you were looking for?

Get in touch and we will add it, or walk you through what it means for your business.

Talk to our teamSee our services
5 ★★★★★ 9 Google reviews