The Email Glossary.

Clear, simple definitions of the terms every developer and marketer needs to know about email delivery, APIs, and authentication.

Blocked Emails

Emails rejected by receiving servers due to IP reputation, blacklisting, or policy restrictions.

Bounce Rate

The percentage of emails that fail to deliver. Hard bounces are permanent, soft bounces are temporary.

Bounced Emails

Emails that could not be delivered. Hard bounces are permanent, soft bounces are temporary.

Click-through Rate (CTR)

The percentage of recipients who click links inside an email.

Dedicated IP vs Shared IP

Dedicated IPs are used only by one sender; shared IPs are used by multiple accounts with shared reputation.

DKIM (DomainKeys Identified Mail)

An authentication method that verifies an email's integrity and sender domain using cryptographic signatures.

DMARC (Domain-based Message Authentication, Reporting & Conformance)

An authentication protocol that builds on SPF and DKIM, telling mail servers how to handle failed authentication.

Email API

A developer interface that allows applications to send and manage emails programmatically without manual SMTP setup.

Email Deliverability

A measure of how successfully emails reach recipients' inboxes instead of spam folders.

Email Service Provider (ESP)

A company or platform that offers tools to send, manage, and track email campaigns, such as AutoSend, Mailchimp, or SendGrid.

Email Warmup

The process of gradually increasing email volume on a new IP or domain to build reputation.

Global Unsubscribes

Addresses that opted out of receiving any emails from your account or domain, across all campaigns and lists.

Inbox Placement

Whether emails land in the primary inbox, promotions tab, or spam folder.

Invalid Emails

Email addresses that don't exist or are incorrectly formatted, causing permanent delivery failures.

List Hygiene

The practice of cleaning email lists by removing invalid or unengaged addresses to improve deliverability.

Marketing Email

Emails sent to promote products, services, or updates to a group of subscribers, including newsletters and promotions.

MX Record

A DNS record that directs emails to the correct mail server for receiving messages.

Open Rate

The percentage of recipients who open an email, influenced by subject line, sender reputation, and placement.

Reported Spam

Addresses that flagged your emails as spam. Automatically suppressed to protect sender reputation.

SMTP (Simple Mail Transfer Protocol)

The standard protocol used to send emails across the internet.

SPF (Sender Policy Framework)

A DNS record that specifies which servers are authorized to send emails for a domain, preventing spoofing.

Suppression List

A list of email addresses that should never receive emails, including unsubscribes, bounces, and spam complaints.

Transactional Email

Automated emails triggered by user actions such as signups, password resets, or purchase confirmations.

Unsubscribe Groups

Categories that allow recipients to selectively unsubscribe from certain types of emails instead of all communication.