Email marketing software glossary and key terms

The software that stores your list and sends your email at scale, with templates, segmentation, automation and reporting. The tools ranked in this category are ESPs.

A person on your list who has given permission to receive your email. Most tools bill by the number of contacts you store, so the size and cleanliness of your list directly drive your cost.

The collection of contacts you send to. Some tools count a contact once across all lists, others count duplicates separately, which can change your bill, so check how a vendor counts before you compare prices.

A filtered slice of your list, such as people who bought in the last 90 days or who clicked a recent email. Segmentation lets you send relevant email and is where engagement and revenue improve.

The permission a subscriber gives to join your list. Single opt in adds them immediately, while double opt in asks them to confirm first; consent is the foundation of both deliverability and compliance.

A two step sign up where the subscriber confirms by clicking a link after joining. It produces a cleaner, more engaged list and fewer spam complaints, at the cost of some sign up drop off.

A subscriber opting out of future email, usually through a required link in the footer. Platforms must honor it promptly, and a healthy unsubscribe rate is part of good deliverability.

A one time email sent to a segment, such as a newsletter or a promotion. Campaigns drive spikes in traffic and sales, while automations drive the steady baseline.

A message or series triggered by an event, such as a welcome sequence or an abandoned cart reminder. Automations do steady work between campaigns and often drive most of a program's revenue.

A pre planned series of emails sent on a schedule after a trigger, such as an onboarding sequence spread over several days. It is one of the most common forms of automation.

A placeholder, such as a first name or a recent purchase, that the tool fills with each subscriber's own data at send time. Personalization tied to good segmentation lifts engagement.

Sending two versions of an email to portions of a segment to see which performs better, then sending the winner to the rest. Useful for subject lines, content and timing.

Automated one to one email tied to an action, such as a receipt, a password reset or a shipping notice. It is often billed and sent separately from marketing email, sometimes through a different product.

The share of your emails that actually reach the inbox rather than the spam folder or a block. It depends on sender reputation, list quality and content, and is the single biggest driver of whether a program works.

A score mailbox providers assign to your sending domain and IP based on past behavior. Low complaints and bounces and steady volume build it; spam traps and high complaints erode it.

Email authentication standards that prove your messages really come from your domain. Mailbox providers increasingly require them, and setting all three up is essential for deliverability.

A sending IP used only by your account, usually offered on higher tiers. It gives you control over your reputation but must be warmed gradually and suits high volume senders, not small lists.

Gradually increasing sending volume on a new IP or domain so mailbox providers learn to trust it. Skipping warm up is a common cause of early deliverability problems after a migration.

The share of delivered emails that were opened. Apple Mail Privacy Protection inflates opens by pre loading images, so treat open rate as a soft signal rather than a hard number.

The share of delivered emails where a recipient clicked a link. It is a more reliable engagement signal than open rate because it reflects a real action rather than a pre loaded image.

An email that could not be delivered. A hard bounce is a permanent failure such as an invalid address; a soft bounce is temporary, such as a full inbox. High bounce rates hurt your reputation.

When a recipient marks your email as spam. Even a small complaint rate damages sender reputation, which is why consent and relevance matter far more than raw list size.

Regularly removing inactive, bouncing or unengaged contacts. It lowers cost on contact based plans and protects deliverability, since a smaller engaged list beats a large stale one.

A campaign, or broadcast, is a one time email you send to a segment, such as a newsletter or a promotion. An automation, or flow, is a message or series triggered by an event, such as a welcome sequence or an abandoned cart reminder. Campaigns drive spikes; automations drive the steady baseline and often most of a program's revenue.

Inbox placement depends on sender reputation, list quality, authentication and content. Emails get filtered when a domain is not authenticated with SPF, DKIM and DMARC, when complaints or bounces are high, when a list contains old or purchased addresses, or when content trips spam filters. Authenticating your domain, keeping a consented list and pruning inactive contacts all improve placement.

Open rates commonly fall in the 20 to 40 percent range, but Apple Mail Privacy Protection inflates opens by pre loading images, so the number is now a soft signal rather than a hard one. Click through rate and revenue per email are more reliable measures of whether your email is working.

Double opt in is a two step sign up where a new subscriber confirms by clicking a link after joining. It produces a cleaner, more engaged list and reduces spam complaints, at the cost of some sign up drop off. It is optional in the US but often worth using; some regions and senders treat it as best practice for consent.

One email when the rankings move. The shortlist, the tradeoffs, the price changes. No filler.