Email glossary

Sending two versions of an email to random parts of a list to see which performs better on one chosen metric.

A triggered email sent to a shopper who added items to a cart but did not complete the purchase.

The part of a message or web page visible without scrolling.

The share of sent messages that the receiving mail server accepted rather than rejected.

Machine-learning tools used to draft copy, suggest subject lines, choose send times or filter spam.

An extra address that delivers into an existing mailbox.

A second address a person gives as a backup way to reach them.

A format that lets an email contain interactive elements such as forms and carousels.

An application programming interface: a defined way for one program to ask another to do something.

Authenticated Post Office Protocol: an optional POP3 login method that uses a challenge-response instead of sending the password directly.

Moving a message out of the inbox into long-term storage without deleting it.

A file sent along with an email message.

Messages a system sends on a trigger or schedule without anyone sending them by hand.

A set of triggers, conditions, delays and actions that sends a series of emails on its own.

A loose marketing term for email that keeps sending on its own once it is set up.

An automatic reply or fixed series of messages sent in response to an event such as a signup or an incoming email.

Bounce messages sent to an innocent address because spam used it as a forged sender.

A way of writing binary data as plain text characters.

Blind carbon copy: recipients added in BCC receive the message without being shown to the others.

An email triggered by something a person did, such as viewing a product or clicking a link.

Brand Indicators for Message Identification: a way to show a brand logo beside authenticated messages in supporting mail clients.

A list of IP addresses or domains that mail receivers use to reject or flag mail; now more often called a blocklist.

Being added to a blocklist, or the act of adding a sender to one.

A list of senders, usually IP addresses or domains, that receivers refuse or treat with suspicion.

Techniques that tell automated visitors from people, used on forms and when measuring email engagement.

A message that could not be delivered and was returned to the sender with a reason.

The percentage of sent messages that bounced.

Email sent from an address on your own domain with a consistent name, rather than from a free-mail account.

The same message sent to a large number of recipients at once.

A throwaway address made to receive one message or one signup and then be abandoned.

The single thing you ask the reader to do next, usually a button or link.

The United States law that sets rules for commercial email, including honest headers, a postal address and a working opt-out.

A saved, ready-made message you reuse instead of writing the same reply each time.

Canada’s Anti-Spam Legislation, which requires consent before you send commercial electronic messages.

A mail domain set up to accept messages for any address at that domain, whether or not a mailbox exists.

Carbon copy: recipients added in CC receive the message and every recipient can see who else got it.

The California Consumer Privacy Act, which gives California residents rights over personal information that businesses collect, including email addresses.

A conversational AI assistant from OpenAI that people use to draft and edit email copy.

The percentage of delivered messages in which a recipient clicked a link.

Clicks divided by a base such as delivered messages or impressions; in email it is usually the click rate.

Unique clicks divided by unique opens: how many of the people who opened also clicked.

A first message to someone you have no prior relationship with, sent for a business purpose.

A message whose primary purpose is to advertise or promote a product, service or business.

Writing a new message, as opposed to replying or forwarding.

A message sent after an action, either to confirm it happened (an order) or to ask the person to confirm an address.

A web form that lets visitors send you a message without opening their own mail app.

The set of people and addresses you send email to.

The share of recipients who complete the goal you set, such as a purchase or a signup.

Customer relationship management software that stores contacts and their interactions.

Email sent or logged through a CRM, so conversations attach to the contact record.

The person responsible for the quality and structure of data in the CRM.

Your own domain used for sending and for links and images in email, instead of the provider’s shared domain.

A distributed denial-of-service attack: many machines flood a service with traffic until it cannot respond.

A sending IP address used by only one sender.

How reliably your email reaches recipients’ inboxes rather than bouncing or landing in spam.

An address on a service built for short-lived use, often with no signup.

DomainKeys Identified Mail: a signature your sending system adds to each message, which receivers check against a public key in DNS.

Domain-based Message Authentication, Reporting and Conformance: a DNS policy that tells receivers what to do with mail that fails SPF and DKIM alignment with your From domain.

A DNS record that holds free-form text.

How mailbox providers rate a sending domain, based on its history of complaints, bounces, spam traps and authentication.

A signup process where the person confirms their address by clicking a link in a message you send after they subscribe.

A series of messages sent over time, on a schedule or triggered by what a person does.

An email whose content differs per recipient, from simple merge fields to blocks that change with data.

Electronic mail: messages sent between mailboxes over the internet using standard protocols.

The string that identifies a mailbox, in the form local-part@domain.

The header fields of a message that hold addresses: From, To, Cc, Bcc, Reply-To and Return-Path.

Measuring what happens after you send: bounces, opens, clicks, conversions, unsubscribes and complaints.

Adding missing email addresses to existing customer records by matching them against a data provider.

Records and signatures (SPF, DKIM, DMARC) that let receivers check a message really came from the domain it claims.

An informal name for sending the same message to your whole list at once.

The rules your system follows when a message bounces.

How often and at what spacing you send to the same people.

A planned set of messages sent to an audience to reach a goal, on a schedule.

How you collect addresses: signup forms, checkout fields, popups, lead magnets and offline sign-up sheets.

Whether upper and lower case matter in an address.

A tool that tests whether an email address is valid and can receive mail.

The software a person uses to read and write email, such as a webmail site, a desktop app or a phone app.

Following the laws and provider rules that apply to your email: consent, sender identification, opt-out and data protection.

Writing the words of an email: subject, preview text, body and call to action.

Putting a campaign live: the final checks and the send.

The part of an address after the @, which decides where mail for that address is delivered.

A tool for designing and building the HTML of an email, from drag-and-drop builders to code editors.

Protecting message content from being read by anyone but the intended parties.

How recipients respond to your messages: replying, clicking, opening and forwarding.

The habits that make email easier to read and respond to: clear subjects, short messages and careful use of reply-all.

A tool that pulls strings that look like email addresses out of text, files or web pages.

When recipients stop paying attention or unsubscribe because they get too much email.

How incoming mail is sorted into the inbox, spam or other folders.

A tool that works out or looks up the address of a named person at a company.

The bottom block of a message with sender details, a postal address and an unsubscribe link.

Passing a received message on to another address, by hand or by an automatic rule.

A server or service at the edge of an organisation’s mail system that filters inbound and outbound messages.

Collecting addresses in bulk from websites and other public sources with automated programs.

The lines of metadata at the top of a message: From, To, Date, Subject, Message-ID and the Received lines each server adds.

A service that provides mailboxes for your domain.

The ongoing work of keeping a list accurate.

Loading a list into a sending tool or CRM.

Everything that sends your mail: domains, sending IPs, mailboxes, DNS records and the platform.

Connecting an email tool with other systems, such as a CRM, a form builder or a store.

Information about an address beyond whether it is valid, such as its provider type and risk flags.

The main legal regimes that govern commercial email.

How content is arranged inside a message.

Using email to find and win new prospects, through signup forms, lead magnets and outreach.

The stages a contact moves through: subscribe, onboard, active, at risk, lapsed and win-back.

A group of subscribers you send to, usually organised into lists, segments and tags.

Records of what happened to each message: accepted, deferred, delivered or bounced, with the reason.

Handling the flow of email in a team or business, from shared inboxes and assignment to lists and sending accounts.

Using email to reach an audience that has agreed to hear from you, to inform, sell or retain.

The numbers used to judge email: delivery, bounce, open, click, conversion, unsubscribe and complaint rates.

Moving mailboxes or lists from one provider or platform to another.

A regular message with news or content sent to subscribers, usually on a fixed schedule.

An automatic message that alerts a person to something that happened, such as a comment, a login or a shipped order.

A short code sent by email to prove a person controls an address or to log them in.

Software that reads incoming messages and extracts structured data, such as order details or lead fields.

Tailoring a message to its recipient, from a name to content chosen by their behaviour.

Software for sending email at scale, with lists, templates, automation and reports.

Written rules for how an organisation sends and handles email.

A page where subscribers choose which messages they get and how often.

The local part of an address, the text before the @.

A standard way for systems to exchange mail: SMTP to send, IMAP and POP3 to read.

The waiting line of outbound messages a server or platform processes.

Limits on how many messages or requests are allowed in a period.

A server that accepts mail and passes it on to another server.

How an email client draws the HTML of a message.

Summarising results for the people who decide: what was sent, what happened and what to change.

The overall trust mailbox providers place in a sender, combining the reputation of its domain and its sending IPs.

Emailing people who showed interest, such as by visiting a page or leaving a cart, to bring them back.

Return on investment for email: how much you earned compared with what you spent.

How a message finds its way from sender to mailbox.

Protecting email accounts and messages from abuse.

Splitting a list into groups so each gets messages that suit it.

The identity a message comes from: the From name, the From address and the envelope sender that receives bounces.

An ordered set of messages sent to one contact, with rules for when it stops.

Software that sends, receives and stores email for a domain.

A block at the end of a message with the sender’s name, role and contact details.

Forging the sender of a message so it appears to come from someone else.

The published specifications that email systems follow.

A plan for what your email is for, who it goes to and how you will judge it.

Reusable message layouts that you fill with content.

Checking a message before it goes out.

A conversation of related messages that a client groups together.

When you send: the day, the hour and the spacing between messages.

An event that starts an automated email, such as a signup, a purchase or a page visit.

The main kinds of email by purpose: transactional, promotional, newsletter, triggered and cold outreach.

Checking that an address is correctly formed.

Placeholders in a template that are replaced with each recipient’s data when the message is sent.

Checking whether an email address can actually receive mail, without sending a message to it.

Gradually raising your sending volume from a new domain or IP so providers learn to trust it.

Malware that spreads by emailing copies of itself to the contacts it finds on an infected machine.

A service where a mailbox provider sends you a report each time one of its users marks your message as spam.

A message sent after an earlier one got no reply or no action.

The display name shown beside the sender’s address in the inbox.

The EU General Data Protection Regulation, which governs how personal data, including email addresses, is collected and used.

A unit of storage, about a billion bytes, used for mailbox size and attachment limits.

Google’s email service, used with a free gmail.com address or on a custom domain through Google Workspace.

A tool for sending mass email from a Gmail account.

A free email provider popular in Germany and other European countries.

Google’s online spreadsheet, commonly used to collect and share contact lists.

Google’s business suite, which hosts company email on a custom domain among other services.

The store where add-ons for Google Workspace apps, such as Gmail and Sheets, are listed and installed.

An anti-spam method where a server temporarily rejects the first message from an unknown sender and accepts a later retry.

A permanent delivery failure, such as an address that does not exist.

Email campaigns tied to seasonal peaks such as year-end or summer sales.

A trap used against abuse: either a hidden form field that bots fill in, or an address that exists only to catch spam senders.

The name of a server, such as mail.example.test.

A message formatted with HTML rather than plain text.

The opening line of a cold message that shows why you are writing to this person.

A mail client setting that does not load images in a message until the reader allows it.

Internet Message Access Protocol: how a mail client reads mail that stays stored on the server.

An IMAP extension that keeps a connection open so the server can tell the client at once when new mail arrives.

Email that arrives at your system, as opposed to email you send.

Attracting people with content they look for, so they come to you and give you their address.

The folder where new messages arrive for a mailbox.

The share of your messages that land in the main inbox rather than spam or another folder.

A personal habit of keeping the inbox empty by processing each message once.

The number that identifies a machine on the internet, which is how mail servers are known to each other.

How receivers rate a sending IP address from its past mail.

Raising the volume sent from a new IP address in steps so receivers learn to trust it.

The web page a person reaches after clicking a link in an email.

Lightweight Directory Access Protocol: a standard way to look up entries in a directory of people and resources.

Sending a prospect a series of useful messages over time until they are ready to talk or buy.

The Liquid template language, used by several e-commerce and email tools to insert data into messages.

A list losing its responsiveness over time as people age out, lose interest or get too much mail.

A message header that lets mail apps show an unsubscribe button next to your message.

A flood of messages aimed at one inbox to bury it or knock it out.

Messages passing back and forth between systems without end, usually from two auto-replies answering each other or a bad forwarding rule.

Combining one template with a table of recipients to produce a personalised message for each row.

A widely used email marketing platform for lists, campaigns and automation.

The automatic sender name on bounce messages that a mail server generates.

A link that opens a new email to a given address, written as mailto:name@example.test.

Multipurpose Internet Mail Extensions: the standard that lets email carry attachments, non-English text and several versions of the same message.

An open-source markup language that compiles into responsive HTML for email.

Mail Transfer Agent: server software that moves messages between mail servers.

Mail User Agent: the program a person uses to read and write email, such as a mail app.

Reaching people through several channels, such as email, SMS, social and ads, with each channel run on its own.

Testing several elements at once, such as a subject, an image and a button, to see which combination works best.

A DNS record that names the mail servers for a domain and their priority.

A sender address such as noreply@ that is not meant to receive answers.

Using shared customer data so every channel, including email, gives one consistent experience.

The first messages a new user or customer receives, to help them get started.

The percentage of delivered messages that were opened.

A person’s active agreement to receive your email.

A person’s choice to stop receiving your email, or a system where you may send until they say stop.

A transactional message sent after a purchase with the order details.

An automatic reply sent while the recipient is away.

Reaching out to people who have not asked to hear from you, such as through cold email or ads.

The folder that holds messages waiting to be sent.

Microsoft’s email client and the service behind outlook.com addresses and Microsoft 365 business mail.

A recipient forwarding your message to someone else.

A fraudulent message designed to trick a person into giving away credentials or money.

A message with no formatting, images or links to styled elements.

Post Office Protocol version 3: a way for a mail client to download messages from a server.

The standard mailbox, postmaster@yourdomain, that a mail domain should keep for reporting delivery problems; also the name of providers’ sender dashboards.

The short line of text that shows after the subject in the inbox list.

The main address on an account or contact record.

Gmail’s main inbox tab, as opposed to Promotions, Social and Updates.

A message that advertises or sells something.

An address that forwards to a person’s real mailbox so the real one stays private.

The file format Outlook uses to store mail, contacts and calendar items offline.

Malware that encrypts a victim’s files and demands payment to unlock them.

A message aimed at contacts who have not engaged for a long time.

Checking an email address at the moment it is entered, before it is saved.

The address a message is delivered to.

Answering to the sender and every other recipient of a message.

A header that tells the recipient’s mail app where replies should go.

The address where bounces and delivery notices are sent, also called the envelope sender.

Text with formatting, such as bold, italics, lists and links.

An address for a function or team rather than a person, such as info@, sales@ or support@.

Secure/Multipurpose Internet Mail Extensions: a way to sign and encrypt email using certificates.

A sending IP address used by several senders, typical of email platforms.

Adding a person to a list as soon as they submit their address, with no confirmation step.

Simple Mail Transfer Protocol: the standard for sending email between servers and from clients to servers.

A temporary delivery failure, such as a full mailbox or a busy server.

Unwanted bulk email: mail sent to people who did not ask for it, as judged by recipients and mailbox providers.

A recipient marking your message as spam; the provider may pass it back to you as a complaint.

An address set up to catch senders who collect or keep addresses without care.

Apache SpamAssassin, an open-source filter that scores a message against many rules.

Sender Policy Framework: a DNS record listing the servers allowed to send mail for a domain.

Secure Sockets Layer, the old protocol for encrypting connections; today the name is often used for its successor, TLS.

The line that tells the reader what a message is about, shown in the inbox.

A list of addresses you must never send to: unsubscribes, hard bounces and complaints.

The specific group of people a message is meant for.

The page shown after someone submits a form.

Inserting a message into an existing email conversation so it looks like a legitimate reply.

A tiny image in an email that records when a message is opened.

A message triggered by a person’s own action or account activity, such as a receipt or a password reset.

Registering domains that look like real ones, such as a common misspelling, to catch mistyped mail or trick people.

The standard that gives every character, in every language, a number so text can be shared between systems.

The percentage of delivered messages that led to an unsubscribe.

Unique selling proposition: the one clear reason someone should choose you over alternatives.

An address that is correctly formed and that the receiving server will accept mail for.

Messages that a service sends to a web address you provide when something happens, instead of you asking repeatedly.

Email that you read and write in a web browser, such as Gmail on the web or Outlook.com.

The first message a new subscriber or customer gets, sent straight after they join.

A list of senders a recipient or system has approved so their mail is not filtered; now often called an allowlist.

A service that connects web apps so an event in one triggers an action in another, without code.