Glossary
The email terms that matter
Plain-English definitions of the terms you'll hear in our docs, our dashboards, and from your deliverability consultant.
- DKIM
- DomainKeys Identified Mail. A cryptographic signature in your email's headers that proves it was authorized by your domain.
- SPF
- Sender Policy Framework. A DNS record that lists the IPs allowed to send mail for your domain.
- DMARC
- Domain-based Message Authentication, Reporting & Conformance. A DNS record that tells mailbox providers what to do when SPF or DKIM fails.
- Bounce
- A failed delivery. Hard bounces are permanent (invalid address). Soft bounces are temporary (mailbox full, server down).
- Complaint
- When a recipient marks your email as spam. Mailbox providers send these back via feedback loops.
- FBL
- Feedback Loop. The mechanism by which mailbox providers forward complaints back to senders.
- Suppression
- A persistent record that prevents future sends to an address. Auto-populated on hard bounce, complaint, and unsubscribe.
- Warmup
- The gradual ramp of send volume on a new IP. Lets mailbox providers learn your sending pattern without flagging spikes.
- Reputation
- The trust score mailbox providers assign your sending IP and domain. Driven by complaint rate, bounce rate, and engagement.
- Postmaster Tools
- Free dashboards from Gmail, Yahoo, and Outlook that show your reputation from their perspective.
- Inbox placement
- The percentage of your delivered email that lands in the inbox rather than spam or promotions.
- MTA-STS
- A standard requiring TLS for incoming mail to your domain. Modern transport security.
- TLS-RPT
- A reporting mechanism for TLS failures on your inbound mail.
- BIMI
- Brand Indicators for Message Identification. Display your logo next to your email in supported clients.
- DSN
- Delivery Status Notification. A standard format for bounce messages.
- Spam trap
- An email address operated by an anti-spam organization or mailbox provider to catch senders with poor list hygiene.
- Catch-all
- A mailbox configuration that accepts every local-part. Risky to send to because you can't verify the address.
- IP pool
- A group of sending IPs treated as one reputation unit. Useful for separating transactional from marketing.