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Email marketing glossary: the terms in plain English

Every word you are likely to meet in an email platform, a report or an audit, explained in a sentence or two. Grouped by where you will run into them, not alphabetically.

List and permission terms

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List
Everyone you can email. Most platforms call the people on it contacts, profiles or subscribers.
Segment
A slice of the list chosen by a rule, such as "bought in the last 90 days" or "never opened". Segments update themselves as people change.
Single opt-in
Someone joins the list as soon as they submit the form.
Double opt-in
Someone joins only after clicking a link in a confirmation email. Fewer sign-ups, fewer fake addresses.
Soft opt-in
A UK rule that lets you email existing customers about similar products without separate consent, as long as you gave them a clear chance to opt out when they bought. See UK email marketing law.
Unsubscribe
Someone asking to stop receiving marketing email. It must be easy and it must be honoured.
Suppression list
Addresses the platform will not send to, such as unsubscribes, hard bounces and complaints.

Sending and deliverability terms

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Deliverability
Whether your email reaches the inbox rather than the spam folder or nowhere at all.
Sending domain
The domain your email comes from, such as yourshop.co.uk. Sending from your own domain is now expected by Gmail and Yahoo.
SPF
A DNS record listing which services are allowed to send email for your domain.
DKIM
A digital signature added to each email that proves it came from your domain and was not changed on the way.
DMARC
A DNS record telling inboxes what to do with email that fails SPF or DKIM checks. Required for bulk senders since 2024, explained in the sender requirements guide.
Sender reputation
How mailbox providers rate you, based on complaints, bounces and engagement. Good reputation means inbox placement.
Hard bounce
An email that could not be delivered because the address does not exist. Remove it straight away.
Soft bounce
A temporary failure, such as a full inbox. Platforms retry, then suppress after repeated failures.
Spam complaint
Someone pressing "report spam". The most damaging number in your report.

Seeing terms like these in your own account and not sure what they mean for you? The free audit explains it in writing.

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Automation terms

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Flow
A set of automated emails that starts when someone does something. Also called an automation, workflow or sequence.
Trigger
The event that starts a flow, such as signing up, placing an order or leaving the basket.
Delay
The wait between flow emails, such as "two days after the first email".
Conditional split
A fork in a flow that sends people down different paths, such as first-time buyers one way and repeat buyers another.
Flow filter
A rule that removes people from a flow, such as "has placed an order since starting".
Welcome series
The flow new subscribers receive. See the welcome series page.
Abandoned cart
A flow that reminds someone who started checkout but did not pay.
Browse abandonment
A flow for someone who looked at a product but did not add it to the basket.
Winback
A flow for past customers who have not bought in a long time.

Campaign terms

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Campaign
A one-off email you send to a list or segment on a day you choose. Some platforms call it a broadcast or single send.
Subject line
The headline in the inbox. Decides whether the email gets opened.
Preview text
The line after the subject line in most inboxes. If you leave it blank, the inbox shows whatever text comes first.
A/B test
Sending two versions to small parts of the list and sending the better one to the rest.
Dynamic content
Parts of an email that change for each reader, such as their name or products they viewed.
Sending window
The time of day a campaign goes out.

Reporting terms

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Open rate
The share of delivered emails that were opened. Inflated by Apple Mail Privacy Protection, so read it with care.
Click rate
The share of delivered emails where someone clicked a link.
Click-to-open rate
Clicks divided by opens. Tells you how well the content worked for people who opened.
Conversion rate
The share of recipients who placed an order the platform credits to the email.
Attributed revenue
Sales the platform credits to an email, based on its attribution window.
Attribution window
How long after an open or click a sale still counts towards an email.
Revenue per recipient
Attributed revenue divided by the number of people the email was sent to. The fairest way to compare emails.

How to use these numbers to make decisions is on reading your numbers.

Questions people ask

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What is the difference between a flow and a campaign?

A campaign is sent once, by you, on a chosen day. A flow sends itself to each person when they do something, and keeps running.

Do I need SPF, DKIM and DMARC?

Yes, if you send marketing email from your own domain. Gmail and Yahoo expect all three from bulk senders, and they help every sender reach the inbox.

What is a good open rate?

It depends on the platform, the list and the share of Apple Mail users, so comparing with averages is unreliable. Compare your own emails with each other instead.

Is a segment the same as a list?

No. A list is who you can email. A segment is a filtered view of that list, which updates as people change.

Read next

Start hereNew to emailThe five things you need first and the first 90 days.GuideWhat email marketing isCampaigns and automation, explained.GuideReading your numbersWhich numbers matter and which to ignore.
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