# Email Bump Email Glossary

> In-depth definitions for email deliverability, authentication, audience, automation, messaging, and measurement.

**Canonical page:** [https://emailbump.com/glossary](https://emailbump.com/glossary)

Each entry explains the term, why it matters, how it works, common mistakes, key takeaways, related definitions, relevant guides, and primary sources.

## Definitions

- [Click-through rate (CTR)](https://emailbump.com/glossary/click-through-rate.md) — The percentage of delivered messages that produced at least one tracked link click.
- [Domain-based Message Authentication, Reporting, and Conformance (DMARC)](https://emailbump.com/glossary/dmarc.md) — An alignment, policy, and reporting layer that connects SPF or DKIM to the visible From domain.
- [DomainKeys Identified Mail (DKIM)](https://emailbump.com/glossary/dkim.md) — A cryptographic signature that lets a domain take responsibility for selected message content.
- [Double opt-in](https://emailbump.com/glossary/double-opt-in.md) — A subscription process that requires a person to confirm control of the submitted email address.
- [Email authentication](https://emailbump.com/glossary/email-authentication.md) — The DNS and cryptographic mechanisms receivers use to verify sending identities and domain authorization.
- [Email automation](https://emailbump.com/glossary/email-automation.md) — A system that sends or changes email journeys in response to time, customer state, or events.
- [Email blocklist (DNSBL / RBL)](https://emailbump.com/glossary/email-blocklist.md) — A published or private dataset of IPs or domains associated with unwanted or risky email.
- [Email deliverability](https://emailbump.com/glossary/email-deliverability.md) — The ability to reach the part of the mailbox where a wanted recipient can find and act on an email.
- [Email segmentation](https://emailbump.com/glossary/segmentation.md) — The practice of selecting recipients using shared attributes, consent, lifecycle state, or behavior.
- [Email subject line](https://emailbump.com/glossary/subject-line.md) — The brief message label that tells a recipient what an email is about before opening.
- [Hard bounce](https://emailbump.com/glossary/hard-bounce.md) — A permanent delivery failure, commonly caused by an invalid address or a definitive policy rejection.
- [Inbox placement](https://emailbump.com/glossary/inbox-placement.md) — Where accepted email is placed, such as the primary inbox, another inbox tab, spam, or junk.
- [IP reputation](https://emailbump.com/glossary/ip-reputation.md) — The sending history and risk signals mailbox providers associate with an IP address.
- [List hygiene](https://emailbump.com/glossary/list-hygiene.md) — The ongoing practice of keeping audience permission, reachability, source, and engagement data trustworthy.
- [One-click unsubscribe](https://emailbump.com/glossary/one-click-unsubscribe.md) — A standards-based HTTPS mechanism that lets a mailbox provider submit an unsubscribe request without a login or confirmation page.
- [Open rate](https://emailbump.com/glossary/open-rate.md) — The share of delivered messages for which the sender recorded at least one tracking-pixel load.
- [Sender name](https://emailbump.com/glossary/sender-name.md) — The display name shown beside an email address to identify the person, brand, or team sending.
- [Sender Policy Framework (SPF)](https://emailbump.com/glossary/spf.md) — A DNS policy that authorizes IP addresses to use a domain in the SMTP envelope.
- [Sender reputation](https://emailbump.com/glossary/sender-reputation.md) — A receiver-specific assessment of sending identity and behavior used when filtering email.
- [Soft bounce](https://emailbump.com/glossary/soft-bounce.md) — A temporary delivery failure that may succeed when retried under a controlled policy.
- [Spam complaint](https://emailbump.com/glossary/spam-complaint.md) — A recipient signal that a message is unwanted, usually created by marking it as spam or junk.
- [Suppression list](https://emailbump.com/glossary/suppression-list.md) — A durable do-not-send control containing recipients or destinations that must not receive certain email.
- [Transactional email](https://emailbump.com/glossary/transactional-email.md) — A message triggered by an individual action, account event, or existing transaction.