Email Marketing Glossary: 50+ Key Terms Every Marketer Should Know

Email marketing has its own vocabulary. Whether you're just starting out or looking to brush up on terminology, this glossary covers the essential terms you'll encounter when running email campaigns.

A

A/B Testing (Split Testing)

A method of comparing two versions of an email to determine which performs better. Variables can include subject lines, send times, content, design, or countdown timer styles. One version is sent to a subset of your list, and the winner is sent to the rest.

Above the Fold

The portion of an email visible without scrolling. Critical for first impressions — place your most important content and call-to-action here. Countdown timers placed above the fold typically see higher engagement.

Allowlist (Whitelist)

A list of approved senders whose emails bypass spam filters. Encouraging subscribers to add your address to their allowlist improves deliverability.

Authentication

Technical protocols (SPF, DKIM, DMARC) that verify an email was sent by an authorized sender. Proper authentication prevents spoofing and improves inbox placement.

B

Bounce Rate

The percentage of sent emails that couldn't be delivered. Hard bounces are permanent failures (invalid address). Soft bounces are temporary issues (full inbox, server down). Keep bounce rate below 2% to maintain sender reputation.

Broadcast Email

A one-time email sent to all subscribers or a segment at the same time. Used for announcements, promotions, or newsletters. Contrast with automated/triggered emails.

C

CAN-SPAM Act

US federal law (2003) governing commercial email. Requires accurate header information, clear opt-out mechanism, physical mailing address, and honest subject lines. Penalties up to $50,120 per violation. See also: GDPR vs US Privacy Laws.

Click-Through Rate (CTR)

The percentage of email recipients who clicked on one or more links in your email. Calculated as: (clicks ÷ delivered emails) × 100. Industry average is 2-5% depending on sector.

Conversion Rate

The percentage of email recipients who completed the desired action (purchase, registration, download). The ultimate measure of email campaign effectiveness.

Countdown Timer

An animated image (typically a GIF) embedded in an email that displays a real-time countdown to a deadline. Updates every time the email is opened. Proven to increase urgency and boost engagement rates. See how countdown timers work.

CTA (Call to Action)

A button or link prompting the recipient to take a specific action — "Shop Now", "Register Today", "Claim Your Offer". Effective CTAs are clear, urgent, and visually prominent.

D

Dedicated IP

An IP address used exclusively by one sender. Gives full control over sender reputation but requires consistent sending volume. Contrast with shared IP.

Deliverability

The ability of an email to reach the recipient's inbox (not spam/junk folder). Affected by sender reputation, authentication, content quality, and image handling.

DKIM (DomainKeys Identified Mail)

An email authentication method that adds a digital signature to outgoing emails. The receiving server verifies the signature against a public key in DNS to confirm the email wasn't tampered with.

DMARC

Domain-based Message Authentication, Reporting, and Conformance. A policy that tells receiving servers what to do when SPF or DKIM checks fail (none, quarantine, or reject).

Double Opt-In

A subscription process requiring email confirmation after initial signup. The subscriber enters their email, then clicks a verification link. Produces higher-quality lists and is recommended for GDPR compliance.

Drip Campaign

An automated email sequence sent over time based on triggers or schedules. Used for onboarding, nurturing leads, or product launch sequences.

E

Email Client

The software or app used to read emails — Gmail, Outlook, Apple Mail, Yahoo Mail, Thunderbird. Each renders HTML and images differently, making cross-client testing essential.

Email Service Provider (ESP)

A platform for sending bulk email campaigns — Mailchimp, Klaviyo, HubSpot, Brevo, etc. ESPs provide list management, templates, analytics, and deliverability infrastructure. See CountHub integration guides.

Engagement Rate

A composite metric measuring how actively subscribers interact with your emails. Combines open rate, click rate, replies, and forwards. High engagement signals to inbox providers that your emails are wanted.

F

FOMO (Fear of Missing Out)

A psychological driver where people fear being excluded from a positive experience. Countdown timers leverage FOMO by visualizing a shrinking opportunity window. Learn more about the psychology of urgency.

G

GDPR (General Data Protection Regulation)

EU regulation (2016/679) governing personal data processing. For email marketing, it requires explicit consent, data minimization, right to erasure, and lawful basis for processing. Applies to any business targeting EU residents. See our GDPR compliance guide and security page.

GIF (Graphics Interchange Format)

An image format supporting animation. Email countdown timers use animated GIFs because they work in virtually all email clients without JavaScript. CountHub generates GIFs server-side on every email open for real-time accuracy.

H

Hard Bounce

A permanent email delivery failure — invalid address, non-existent domain, or blocked recipient. Hard bounced addresses should be immediately removed from your list.

HTML Email

An email formatted with HTML code, allowing rich layouts, images, colors, and interactive elements. Most marketing emails are HTML. Contrast with plain text emails.

I

Inbox Placement Rate

The percentage of delivered emails that land in the primary inbox (not spam, promotions, or other tabs). More meaningful than delivery rate alone.

IP Warming

The practice of gradually increasing email volume from a new IP address to build sender reputation. Sending too much too fast from a new IP triggers spam filters.

L

Landing Page

A dedicated web page that email recipients arrive at after clicking a link. Should match the email's promise and provide a clear path to conversion.

List Hygiene

The practice of regularly cleaning your email list by removing invalid addresses, unengaged subscribers, and spam traps. Essential for maintaining deliverability.

O

Open Rate

The percentage of delivered emails that were opened. Tracked via a tiny invisible pixel. Note: Apple Mail Privacy Protection (MPP) pre-loads tracking pixels, inflating open rates for Apple Mail users since iOS 15.

Opt-In

The process of a subscriber giving consent to receive emails. Can be single (immediate subscription) or double (requires email confirmation). GDPR requires clear, affirmative opt-in for EU subscribers.

P

Personalization

Customizing email content for individual recipients using data like name, purchase history, location, or behavior. Goes beyond "Hi { first_name }" to include dynamic content blocks and tailored recommendations.

Plain Text Email

An email without HTML formatting — just text. Higher deliverability and accessibility. Often used for transactional emails or to appear more personal.

Preheader Text

The preview text shown after the subject line in the inbox. Acts as a "second subject line." Best practice: 40-130 characters that complement (not repeat) the subject line.

R

Responsive Design

Email design that adapts to different screen sizes (desktop, tablet, mobile). Uses CSS media queries to adjust layout, font sizes, and image dimensions. Critical since over 60% of emails are opened on mobile.

S

Scarcity

A persuasion principle where limited availability increases perceived value. In email marketing, scarcity is communicated through countdown timers, limited stock indicators, and exclusive access windows. See psychology of urgency.

Segmentation

Dividing your email list into groups based on shared characteristics — demographics, behavior, purchase history, engagement level. Segmented campaigns consistently outperform broadcast emails.

Sender Reputation

A score assigned to your sending IP/domain by inbox providers based on sending patterns, bounce rates, spam complaints, and engagement. High reputation = better inbox placement.

Soft Bounce

A temporary email delivery failure — full inbox, server temporarily down, message too large. The ESP typically retries delivery. Persistent soft bounces should be investigated.

SPF (Sender Policy Framework)

A DNS record that specifies which servers are authorized to send email from your domain. Helps prevent email spoofing and improves authentication.

Spam Trap

An email address used by inbox providers and blocklist operators to catch senders with poor list hygiene. Hitting a spam trap severely damages sender reputation.

Subject Line

The text displayed in the inbox before an email is opened. The single most important factor in open rates. Best practice: 30-50 characters, clear value proposition, avoid spam trigger words.

T

Transactional Email

An automated email triggered by a user action — order confirmations, shipping notifications, password resets, account alerts. Typically exempt from marketing consent requirements but must still comply with GDPR for data processing.

Trigger Email

An automated email sent in response to a specific action or event — cart abandonment, browse abandonment, milestone reached, or anniversary. Highly targeted and typically outperform bulk emails.

U

Unsubscribe Rate

The percentage of recipients who opt out after receiving an email. Industry average is 0.1-0.5%. Rates above 0.5% suggest content or frequency issues. Note: making unsubscribe easy is legally required (CAN-SPAM, GDPR).

Urgency

A marketing tactic that motivates immediate action by emphasizing time pressure. Created through countdown timers, deadline language, and limited-time offers. Most effective when genuine — false urgency damages trust. See our guide on urgency psychology.

W

Warm-Up (Email)

See IP Warming. The process of gradually building sending reputation on a new IP address or domain.

Welcome Email

The first email sent to a new subscriber after they opt in. Sets expectations, delivers promised content, and establishes the sender-subscriber relationship. Welcome emails have the highest open rates of any email type (typically 50-80%).