A small dictionary of email terms. Short definitions here, longer notes inside each entry.
A
Above the fold is the first part of an opened email that is visible before scrolling. How much fits there depends on the device and email client.
The percentage of emails sent that are successfully accepted by the recipient’s mail server, regardless of whether they land in the inbox or spam folder.
An aha moment is when a new user first recognizes a product’s core value. Teams tie it to a measurable activation action and use lifecycle email to move users toward it.
Apple Mail Privacy Protection (MPP)
Apple Mail Privacy Protection preloads email content and masks IP addresses, which can inflate open rates.
An attachment is a file sent along with an email message, such as a PDF, image, or spreadsheet.
An autoresponder automatically sends an email, or a series of emails, to subscribers based on specific triggers or time intervals.
B
BIMI lets supporting inboxes such as Gmail, Yahoo, and Apple Mail display your brand’s certified logo next to authenticated email once DMARC is at enforcement.
An email blacklist, or blocklist, is a database of IP addresses, domains or URLs flagged for spam. Listed senders can see mail rejected or filtered.
The percentage of your total emails sent that were rejected or returned by the receiving mail server.
C
A call to action (CTA) is the button, link, or line that asks an email reader to take the next step.
CAN-SPAM is the U.S. law for commercial email: accurate headers, honest subject lines, a postal address, and a working opt-out honored within 10 business days.
CASL is Canada’s anti-spam law. Commercial electronic messages need express or implied consent, sender identification, and a working unsubscribe.
The percentage of delivered emails in which the recipient clicked at least one link.
Cold email is unsolicited email sent to someone with no prior relationship. It is not the same as lifecycle, transactional or opted-in marketing email.
CPM = (Spend ÷ Impressions) × 1,000. In email, you see it when buying sponsorship slots or renting a list.
D
The ability of an email to reach an inbox without being blocked or rerouted by spam filters.
DKIM (DomainKeys Identified Mail)
DKIM (DomainKeys Identified Mail) adds a digital signature to each message so receivers can verify it wasn’t altered and really comes from your domain.
DMARC (Domain-based Message Authentication, Reporting & Conformance)
DMARC checks whether SPF or DKIM aligns with the visible From domain and lets its owner request how receivers handle failures.
A two-step process where a person who signs up to receive emails must confirm their email address by clicking a link in a confirmation email.
A method used in direct marketing where a set of predetermined emails are sent out automatically on a schedule.
E
Email authentication is the set of technical checks that proves your mail is really from your domain and has not been tampered with in transit.
Email automation sends messages when defined conditions are met, such as a contact joining your audience, a property changing, an event from your app, or a timer completing.
The main content of an email message, excluding the subject line, header, and footer. It contains the primary message, graphics, links, and other relevant details the sender wishes
to communicate to the recipient.
An email campaign is an individual email message or a coordinated set of email messages that are sent to a segment of contacts with a particular purpose or goal in mind.
The email customer journey maps every email a person receives from signup through renewal, with a trigger, recipient, and stopping condition for each message.
An email flow is an automated email series triggered by user behavior, such as signing up or going inactive, with conditions that stop messages once the task is done.
The bottom section of an email that usually contains sender information, such as company name, contact info, social media links, and unsubscribe links.
An email funnel organizes emails around progress toward one defined outcome, such as a trial start or upgrade, and measures where people stop moving forward.
The top portion of an email that contains essential information such as the sender’s name, email address, subject line, and preview text.
An email list is a stored group of email addresses you send to. The consent behind each address decides what you can send to it.
An email service provider (ESP) is the software you use to send, manage, and measure email to your users, customers, or subscribers.
Email warmup is gradually ramping send volume on a new domain or IP so mailbox providers build a reputation for it. Start low, send at a consistent rate, and grow only while spam and bounce signals stay healthy.
Email engagement is how recipients interact with your emails, including opens, clicks, replies, conversions, unsubscribes, and other response signals.
F
Feedback loops pass spam complaints from mailbox providers back to senders, so complaining contacts can be suppressed when the report identifies them.
H
A hard bounce means an email could not be delivered for a permanent reason, such as an invalid address or a domain that does not accept mail. Suppress the address and stop sending.
Emails that include graphics and colors and look similar to a webpage. They provide a more visually engaging experience than plain text emails.
I
Where your email ends up once it’s delivered: in the primary inbox, spam folder, or another location like Gmail’s Promotions tab.
An IP address is a numeric label that identifies a device on a network. In email, the sending IP carries a reputation with mailbox providers.
IP warming is the gradual increase of email volume from a new or changed sending IP. Start with engaged recipients, raise volume slowly, and watch bounces, deferrals, and spam rate.
L
A landing page is a focused web page designed to convert visitors from an email into a specific action.
The process of developing and reinforcing relationships with potential customers at every stage of the sales funnel through targeted and relevant content.
Email list hygiene is the process of regularly cleaning and maintaining your email list by removing inactive or unengaged subscribers.
List-ID is an email header that identifies which mailing list a message belongs to, helping clients filter and organize subscription mail.
List segmentation groups an email audience by shared properties or activity, such as plan, location or setup progress.
N
A newsletter is a recurring email sent to subscribers with updates, ideas, stories, or resources they chose to receive.
Newsletter open rate measures the percentage of recipients who open a sent newsletter, calculated by dividing unique opens by emails delivered.
A no-reply email address sends from a mailbox that is not monitored, so replies bounce or go unread unless a Reply-To header routes them elsewhere. Use it only where a reply would make no sense.
O
A feature in email marketing that allows recipients to easily opt out of future emails with a single click.
Open rate is the percentage of delivered emails that are opened, offering a top-level indicator of how effectively your subject line and sender name attract attention.
Opt-in is the act of giving consent to receive marketing emails, typically by subscribing via a form or checkbox.
Opt-out is the process by which a subscriber stops receiving emails by unsubscribing, removing their consent to further communications.
P
Permission marketing sends promotional messages to people who have chosen to receive them and respects their decision to stop.
Email personalization uses recipient or event data to change a message. Set fallbacks and test missing values before sending.
A fraudulent attempt, usually via email, to steal personal information or credentials by masquerading as a trustworthy entity.
An email composed solely of text without any formatting, images, or graphics. Unlike HTML emails, it appears the same regardless of the recipient’s email client or platform, ensuring
compatibility.
A preference center is a page where subscribers choose what emails they want to receive, how often they want them, or whether they want to unsubscribe.
Preview Text (or Preheader Text)
Preview text is the inbox snippet shown after an email subject line. Put the key words first, do not repeat the subject, and test how each client truncates it.
A product waitlist is an email list of potential customers who have expressed interest in a product or service that is not yet available to the general public.
A promotional email is a marketing email that aims to promote a product, service, or offer to recipients to drive sales or engagement.
R
An email recipient is the person or mailbox a message is sent to. SMTP envelope addresses govern delivery; visible headers describe the message’s addressees.
A reply-to email address controls where replies go. It can be a different mailbox from the visible From address.
Responsive design refers to designing emails (or websites) so that they automatically adapt and display correctly across various devices and screen sizes.
An email format that allows for basic text formatting, such as different fonts, colors, sizes, and the inclusion of hyperlinks, offering more visual appeal and structure than plain
text emails while being less complex than HTML emails.
S
The email sender name, or From name, is the display name recipients see next to the subject line in the inbox.
A score assigned by Internet Service Providers (ISPs) that can affect your email deliverability.
A one-step process where a person who signs up to receive emails is immediately added to the email list.
Email that is returned to the sender due to a temporary issue, like a full inbox or an offline email server.
Spam, also known as junk mail, refers to unsolicited and often irrelevant or inappropriate email messages sent in bulk to a large number of recipients.
Spam trigger words are phrases spam filters may flag, one signal among many alongside sender reputation and authentication.
SPF (Sender Policy Framework) is a DNS-based email authentication method that lists which servers are authorized to send mail for your domain.
Split Testing (or A/B Testing)
Split testing (A/B testing) sends email variants to separate groups and compares a chosen outcome, such as clicks or completed signups.
A subject line is the short text shown in the inbox that summarizes an email. Put the essential words first, match the body, and test in the clients your audience uses.
A suppression list is a list of contacts who should not receive future email, usually because they unsubscribed, bounced, or complained.
T
Transactional emails serve an account action or transaction, such as a password reset or receipt. Their purpose distinguishes them from marketing email.
U
Unsubscribe rate is the percentage of delivered emails that lead recipients to opt out after receiving a campaign or sequence.
W
A welcome email is the first email a person receives after signing up. It confirms the signup, sets expectations, and points to one next step.
A whitelist (allowlist) is a list of email addresses, domains, or IPs a recipient or mail administrator has marked as trusted so their messages are less likely to be filtered.