The Email Glossary.
Clear, simple definitions of the terms every developer and marketer needs to know about email delivery, APIs, and authentication.
Transactional Email
Automated emails triggered by user actions such as signups, password resets, or purchase confirmations.
Marketing Email
Emails sent to promote products, services, or updates to a group of subscribers, including newsletters and promotions.
SMTP (Simple Mail Transfer Protocol)
The standard protocol used to send emails across the internet.
Email API
A developer interface that allows applications to send and manage emails programmatically without manual SMTP setup.
DKIM (DomainKeys Identified Mail)
An authentication method that verifies an email's integrity and sender domain using cryptographic signatures.
SPF (Sender Policy Framework)
A DNS record that specifies which servers are authorized to send emails for a domain, preventing spoofing.
DMARC (Domain-based Message Authentication, Reporting & Conformance)
An authentication protocol that builds on SPF and DKIM, telling mail servers how to handle failed authentication.
Bounce Rate
The percentage of emails that fail to deliver. Hard bounces are permanent, soft bounces are temporary.
Email Deliverability
A measure of how successfully emails reach recipients' inboxes instead of spam folders.
Inbox Placement
Whether emails land in the primary inbox, promotions tab, or spam folder.
Open Rate
The percentage of recipients who open an email, influenced by subject line, sender reputation, and placement.
Click-through Rate (CTR)
The percentage of recipients who click links inside an email.
Suppression List
A list of email addresses that should never receive emails, including unsubscribes, bounces, and spam complaints.
Global Unsubscribes
Addresses that opted out of receiving any emails from your account or domain, across all campaigns and lists.
Unsubscribe Groups
Categories that allow recipients to selectively unsubscribe from certain types of emails instead of all communication.
Reported Spam
Addresses that flagged your emails as spam. Automatically suppressed to protect sender reputation.
Invalid Emails
Email addresses that don't exist or are incorrectly formatted, causing permanent delivery failures.
Bounced Emails
Emails that could not be delivered. Hard bounces are permanent, soft bounces are temporary.
Blocked Emails
Emails rejected by receiving servers due to IP reputation, blacklisting, or policy restrictions.
Email Warmup
The process of gradually increasing email volume on a new IP or domain to build reputation.
Dedicated IP vs Shared IP
Dedicated IPs are used only by one sender; shared IPs are used by multiple accounts with shared reputation.
List Hygiene
The practice of cleaning email lists by removing invalid or unengaged addresses to improve deliverability.
MX Record
A DNS record that directs emails to the correct mail server for receiving messages.
Email Service Provider (ESP)
A company or platform that offers tools to send, manage, and track email campaigns, such as AutoSend, Mailchimp, or SendGrid.
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