35 Email Marketing Terms Every Marketer Should Know

Last updated: October 2026.

Email marketing terms fall into four groups: the metrics that measure a campaign, the practices that build a list legally, the authentication settings that decide whether you reach the inbox, and the content formats you actually send. In Australia, consent and unsubscribe rules come from the Spam Act 2003, which is enforced by the ACMA.

What do the email marketing metrics mean?

Email marketing metrics measure how many people received, opened, clicked and acted on a campaign, and each one has a formula you can calculate from the same two numbers. Knowing the formula matters because vendor dashboards count some of these differently.

Open rate

Open rate is the percentage of delivered emails that were opened, calculated as unique opens divided by emails delivered, multiplied by 100. It is the metric most affected by privacy changes, so treat it as a soft signal rather than a hard number.

Click through rate

Click through rate is the percentage of delivered emails that produced at least one click, calculated as unique clicks divided by emails delivered, multiplied by 100. It is the most useful single metric for a campaign, because a click is a deliberate human action that privacy features did not change.

Click to open rate

Click to open rate measures how many people who opened the email then clicked, calculated as unique clicks divided by unique opens, multiplied by 100. It answers a different question from click through rate: not how many received it acted, but how compelling the content was for the people who actually looked.

Conversion rate

Conversion rate is the percentage of recipients who completed the action you wanted, such as a purchase or a booking, calculated as conversions divided by emails delivered, multiplied by 100. It is the only metric in this list that maps directly to revenue, which makes it worth setting up properly even when it is small.

Bounce rate, hard and soft

A bounce is an email that could not be delivered, and is calculated as bounced emails divided by emails sent, multiplied by 100. A hard bounce is permanent, usually an address that does not exist, while a soft bounce is temporary and often a full mailbox or a server problem. Hard bounces should be removed immediately, because continuing to send to them damages your reputation.

Unsubscribe rate

Unsubscribe rate is the percentage of recipients who opted out of a specific campaign, calculated as unsubscribes divided by emails delivered, multiplied by 100. A small rise is normal and often healthy, because people who are not interested are leaving rather than reporting you as spam.

Spam complaint rate

Spam complaint rate is the percentage of recipients who marked your email as spam rather than unsubscribing, calculated as complaints divided by emails delivered, multiplied by 100. This is the metric to act on fastest, because mailbox providers use it directly when deciding whether to keep delivering your mail to the inbox.

List growth rate

List growth rate measures whether your list is expanding or shrinking over a period, calculated as new subscribers minus unsubscribes and bounces, divided by the starting list size, multiplied by 100. A list that grows without new sign-ups is usually a sign that your segmentation is wrong rather than that your content is working.

Which consent terms matter when building a list?

List building terms describe how people end up on your list and how you keep that list clean and legal. The consent wording is the part that matters in Australia, because consent is a legal requirement rather than a best practice.

Single opt-in

Single opt-in adds a person to your list as soon as they submit a form, with no confirmation step. It produces a larger list faster and a lower quality one, because typo addresses and deliberate junk submissions go straight in.

Double opt-in

Double opt-in requires the person to confirm by clicking a link in a verification email before they are added. It produces a smaller list with better engagement and a much stronger consent record, which is the record you would rely on if a complaint were ever made.

Lead magnet

A lead magnet is something useful you give away in exchange for an email address, such as a checklist, a calculator or a short guide. The best ones solve a narrow problem completely, because a partial answer creates no reason to hand over contact details.

Segmentation

Segmentation is dividing your list into groups by behaviour, location or interest so each group receives something relevant. Segmenting by what people have already clicked is usually more effective than segmenting by who they are, because it reflects current intent.

Suppression list

A suppression list is a permanent record of addresses that must never be mailed again, including unsubscribes, hard bounces and complaints. It has to survive list imports, which is why an unsubscribe has to be honoured across your whole system rather than removed by hand.

List hygiene

List hygiene is the routine of removing addresses that bounce or never engage, and it protects your deliverability more than any subject line. Mailbox providers judge you on how your recipients behave, so a list full of people who never open is a liability rather than an asset.

Zero party data

Zero party data is information a customer deliberately tells you, such as a preference or a purchase intention, rather than data you infer. It is the most reliable form of personalisation because the person stated it, and it carries clearer consent than anything you collected indirectly.

Which terms decide whether email reaches the inbox?

Deliverability terms describe whether your email reaches the inbox, and authentication is the technical half of that. Setting these records correctly is a one-off job that decides how every future campaign performs, so they are worth getting right early.

SPF

SPF is a DNS record that lists the servers authorised to send email on behalf of your domain, so a receiving server can check whether the sender was allowed to. Without it, anyone can send mail claiming to be your domain and nothing flags it.

DKIM

DKIM adds a cryptographic signature to each message so the receiver can confirm it was not altered in transit. Where SPF checks who sent the mail, DKIM proves the message arrived intact and from the domain that signed it.

DMARC

DMARC ties SPF and DKIM together and tells the receiving server what to do when a message fails both checks, such as quarantining or rejecting it (DMARC.org). It also sends you reports, which is how most businesses first discover that something is sending as their domain.

BIMI

BIMI lets a verified brand logo appear beside your email in the inbox, once DMARC is enforced and the logo is validated. It is a trust signal rather than a deliverability fix, and it requires a clean authentication setup before it can be used at all.

Sender reputation

Sender reputation is the score mailbox providers build about your sending domain and IP address, based on how recipients behave. It is not visible to you in a single number, and it is the sum of complaints, bounces, engagement and how long you have been sending consistently.

Blocklist

A blocklist is a published list of IP addresses or domains that providers have flagged, and appearing on one means your mail is rejected or sent to spam. Most businesses end up there through a purchased list or a compromised account rather than through their own campaigns.

Spam trap

A spam trap is an email address that nobody legitimately owns and that is never subscribed to, used to catch senders who mail lists they should not. Because a trap cannot be subscribed to honestly, hitting one is treated as proof of list problems.

Honeypot

A honeypot is also a trap address, and is often created by an abandoned mailbox that is kept alive precisely to see who keeps mailing it. Mailing a honeypot repeatedly is one of the fastest known ways to lose inbox placement.

IP warm-up

IP warm-up is the practice of increasing send volume gradually on a new IP address so providers learn that your mail is wanted. Sending a large campaign immediately from a new address looks exactly like a spam run, whatever the content says.

Inbox placement

Inbox placement is where your email actually lands, whether that is the main inbox, a promotions tab or the spam folder. It is measured separately from delivery, because a message can be delivered successfully and still never be seen.

Which terms describe an individual campaign?

Campaign and content terms describe the parts of a single email and the ways you send them. These are the terms you will hear most often in a briefing, so they are worth being precise about.

Preheader

The preheader is the short line of text that appears beside or beneath the subject line in most inboxes, and it is drawn from the first text in your email unless you set it deliberately. Leaving it to chance wastes the second most valuable line you have.

Subject line

The subject line is the single line of text a recipient sees before deciding whether to open, and it is the most valuable sentence in the whole campaign. Specific beats clever every time, because a person scanning an inbox needs to know what is inside before they invest a click.

Dynamic content

Dynamic content is email that changes what it shows based on what you know about the recipient, such as their suburb or their past purchases. It is one campaign with several versions rather than several separate campaigns, which is what makes it efficient.

A/B testing

A/B testing sends two versions of a campaign to two portions of your list and compares the results, so a decision is based on data rather than opinion. Test one variable at a time, because changing the subject line and the send time together tells you nothing about which one worked.

Drip campaign

A drip campaign is a series of emails sent on a schedule after a trigger, such as signing up or downloading a guide. It does the follow-up consistently, which is the part most businesses do once and then forget.

Triggered and transactional email

A triggered email is sent in response to a specific action, and a transactional email is one tied to a transaction such as an order confirmation or a password reset. Transactional messages usually achieve far higher open rates than campaigns, because the recipient is expecting them.

What are the email compliance rules in Australia?

Australian commercial email is governed by the Spam Act 2003, which the ACMA enforces, and it applies to any message with a commercial purpose sent from or to Australia (ACMA). Three rules cover most of it, and a business that follows all three is unlikely to have a problem.

Where the other frameworks fit is narrower than most guides suggest. CAN-SPAM applies to commercial email sent to the United States, and the GDPR applies when you process personal data of people in the European Union, so an Australian business with no US or EU recipients is not primarily governed by either (European Commission).

Cold email sits in the gap most people misunderstand. It is not automatically illegal in Australia, but it requires consent that falls within the Act, and a scraped list with no relationship and no basis for inferred consent does not meet that test. The ACMA publishes guidance on what it treats as acceptable sending (ACMA).

Which email marketing term means what?

This reference table condenses the definitions above into one place, grouped by what the term is for. Use it as a quick check rather than a substitute for the sections above.

One more term belongs here because it explains the others. Apple Mail Privacy Protection pre-fetches email content on behalf of the recipient, which can register an open even when nobody looked at the message, and that is the main reason open rate stopped being a metric you can trust (Apple).

What else do marketers ask about these terms?

What is the difference between a hard bounce and a soft bounce?

A hard bounce is permanent and means the address does not exist or will never accept your mail, so it should be removed straight away. A soft bounce is temporary, caused by a full inbox or a busy server, and the address is worth retrying later. Most platforms handle this automatically, but it is worth checking that yours actually suppresses hard bounces rather than retrying them.

Do I need SPF, DKIM and DMARC for a small business?

You need all three if you want reliable inbox placement, and the setup is a one-off task rather than an ongoing one. SPF and DKIM are straightforward to publish, and DMARC can start in a monitoring mode that reports problems without blocking anything. Without them, your mail is easier to spoof and more likely to be filtered.

Is cold email legal in Australia?

Cold email is not automatically illegal in Australia, but it must still meet the consent requirement under the Spam Act, and a purchased or scraped list generally does not. Consent can sometimes be inferred from a clear existing relationship, such as a business contact you have dealt with. Relying on inferred consent for a list of strangers is where most businesses get into trouble.

Why did my open rates suddenly change?

Open rates changed for almost everyone when Apple introduced Mail Privacy Protection, because the feature can register an open whether or not a person read the message. If your list skews towards Apple Mail users, your open rate may have risen without any change in real engagement. Switch your reporting to click based metrics so you are measuring deliberate human action instead.

How many emails should I send each month?

Send as often as you can maintain genuinely useful content, and no more, because unsubscribes and complaints rise when you send without a reason. A consistent monthly email that people open beats a fortnightly one they start ignoring. Watch your spam complaint rate rather than a calendar if you are unsure.

Email marketing rewards precision, and precision starts with knowing the vocabulary well enough to brief a developer, an agency or a platform correctly. The wider set of marketing definitions is in the guide to marketing terms, a longer treatment of the channel is in the ultimate guide to email marketing, and the practical habits are covered in email marketing best practices. For the automation side, see the benefits of workflow automation, the wider range sits under digital marketing services, and you can read about the team behind the work on the DigiFix blog.