Email Marketing Glossary

A glossary of the most important terms and concepts that every email marketer must know.


A/B Split Test

A/B Split Test (often called just A/B Test) is a method of comparing two versions of digital marketing campaigns. A/B split testing gained popularity as a method of comparing performance of different versions of landing pages. However, the method is based on statistical methods that date back to the 18th century. A/B split testing can be used for measuring effectiveness of any type of digital marketing campaign. Read more about A/B Split Testing in our email marketing guide.

Acceptable Spam Report Rate

Acceptable spam report rate is a measure of how many marketing or status emails sent by a particular sender are reported as spam or junk. A generally accepted value among email carriers is 0.1%. Once an IP address from which you send emails reaches a high number of spam reports, subsequent emails sent from this IP will be marked as spam and they will be placed in a junk folder automatically. Even higher spam reports will get the IP blacklisted. You can use a tool like InboxHit Blacklist Check and Monitor to see if your IP address is blacklisted.

Acceptance Rate

ALT tags

ALT tag is an HTML attribute applied to image tags to provide a text alternative for search engines. Search engines and other web crawlers cannot interpret images. However, images can play a crucial part in how people interpret a particular web page. It is very important to include ALT tags in HTML emails because most email clients by default block images. ALT tags provide a description of the image and thus your email recipients can conclude a meaning of the image.

Animated Gif

Animates Gif is an image file format. Animated Gifs are a quick-and-easy way to present dynamic content, especially in web pages and in emails. Animated Gif file sizes are small compared to other alternatives for creating dynamic content like Java and Flash. Therefore, animated Gifs can be downloaded by the browser or email client easily, allowing for a faster user experience.


Attachment is a file that can be sent along with an email. It can be any type of file like a document, an image or a video. When your recipients open your email message, they can double-click on the attachment to open it with the program assigned to that file type on their computer. Normally, email service providers have limits on attachment size. It varies from a provider to provider. Attachments may also include computer viruses, trojans, worms, or other malware.


Autoresponder is email automation software. Autoresponder automatically returns a predefined email reply to anyone who sends an email to a particular email address. Autoresponders can be very simple or they can be quite complex. Simple autoresponders return the same response. Complex autoresponders may analyze actual email and reply with different responses based on the keywords contained in the original email. You can use autoresponders to reply to your visitors instantly with the most common responses.


Behavioral Email



Bounce Rate


Bulk Folder

Bulk Mail



CASL (Canadian Anti-Spam Law)


Complaint Rate

Confidence Level

Contact List

CPD (Clicks Per Delivered)

CPO (Clicks Per Open)

CPM (Cost Per Thousand)

CSS (Cascading Style Sheets)

CTA (Call to Action)

CTR (Click-Through Rate)

Conversion Rate


Dedicated IP

Dedicated Server


Delivery Rate


DKIM (DomainKeys Identified Mail)

Double Opt-In

Drip Marketing

Dynamic Content


Email Analytics

Email Campaign

Email Client

Email Filter

Email Harvesting

Email Phishing

Email Queue

Email Shares

Email Sponsorships



ESP (Email Service Provider)


False positive



Google Analytics


Grey Mail


Hard Bounce


Honey Pot

House List (see Retention List)

HTML Email


Inbox Placement Rate

IP Warmup

ISP (Internet Service Provider)


Landing Page

Levels of Authentication

List Broker

List Churn

List Fatigue

List Growth

List Rental

List Segmentation


Marketing Automation

MIME (Multi-Purpose Internet Mail Extensions)



Open Rate

Opt-In (or Subscribe)

Opt-Out (or Unsubscribe)



Physical Address

Plain Text Email

Pre-Header Text

Preference Center

Privacy Policy

Promotional Emails

Promotions Tab


Read or Open Length


Rental List (or Acquisition List)

Responsive Design




Sender Name

Sender Score

Shared IP

Shared Server

Signature File

Single Opt-In

SMTP (Simple Mail Transfer Protocol)

Soft Bounce

Solo Ads


Spam or UCE (Unsolicited Commercial Email)

Spam Cop


SPF or Sender Policy Framework, is an open standard that allows the owner of a domain to specify which mail servers they use to send mail from that domain. Read more about SPF in our Email Deliverability Guide.

Statistical Relevance

Subject Line


Subscriber Value




Transactional Emails

Triggered Emails


UCE (Unsolicited Commercial Email)

Unique Clicks

Unsubscribe Rate


Welcome Emails


Email Marketing Agencies Cases

Get Started Now

Use InboxHit online solution to boost your email deliverability. Get 1000 welcome credits.

Click your favorite button below for a one-click sign-up.

Google Twitter Facebook LinkedIn

InboxHit provides solutions and services to boost email deliverability, increase email marketing efficiency and achieve 100% innox hit rate. Use InboxHit API to detect disposable emails, block disposable emails, detect and block DEAs, validate email addresses, check if a mailbox exists, reduce bounces, boost deliverability, increase email marketing efficiency, reduce email delivery costs. InboxHit API is also available on RapidAPI.