Glossary
Updated
Email marketing glossary
Short, accurate definitions of the authentication, deliverability, metrics and list terms that decide whether your email reaches the inbox.
- Terms defined
- 18
- Terms defined
- Categories
- 4
- Categories
- Sourced to standards
- RFC
- Sourced to standards
Authentication
- BIMI (Brand Indicators for Message Identification)BIMI (Brand Indicators for Message Identification) is a DNS TXT record that points mailbox providers to your brand logo so they can display it next to authenticated messages.
- DKIM (DomainKeys Identified Mail)DKIM (DomainKeys Identified Mail) is a cryptographic signature added to each email's headers.
- DMARC (Domain-based Message Authentication, Reporting and Conformance)DMARC is a DNS TXT record at _dmarc.yourdomain.com that tells receivers what to do with mail that claims to be from your domain but fails authentication.
- SPF (Sender Policy Framework)SPF (Sender Policy Framework) is a DNS TXT record that lists which servers may send email using a domain in the envelope sender (Return-Path).
Deliverability
- Email deliverabilityEmail deliverability is the ability of your emails to reach recipients' inboxes rather than bouncing or landing in spam.
- Email warmupEmail warmup is the practice of gradually increasing sending volume from a new domain or IP address so mailbox providers can build a positive reputation for it before you send at full volume..
- Hard bounceA hard bounce is a permanent delivery failure: the receiving server rejected the email and retrying will not help.
- MX record (Mail Exchanger)An MX (Mail Exchanger) record is a DNS record that names the servers that accept incoming email for a domain, each with a priority number.
- Sender reputationSender reputation is the trust score mailbox providers assign to your sending domain and IP addresses, based on how recipients and their systems react to your mail.
- Soft bounceA soft bounce is a temporary delivery failure: the receiving server deferred the email but the address may accept it later.
- Transactional emailTransactional email is a one-to-one message triggered by a user's action or account event, such as a password reset, login code, receipt or shipping notice.
Metrics
- Bounce rateEmail bounce rate is the percentage of sent emails that the receiving server rejected as undeliverable.
- Click-through rate (CTR)Email click-through rate (CTR) is the percentage of delivered emails in which at least one link was clicked.
- Open rateEmail open rate is the percentage of delivered emails that were opened at least once.
- Spam complaint rateSpam complaint rate is the percentage of delivered emails that recipients reported as spam.
List management
- Double opt-inDouble opt-in (confirmed opt-in) is a signup process where a new subscriber must click a link in a confirmation email before they are added to the list.
- List hygieneList hygiene is the routine of removing or suppressing email addresses that hurt deliverability: hard bounces, spam complainers, long-inactive subscribers, invalid addresses and likely spam traps..
- One-click unsubscribe (RFC 8058)One-click unsubscribe is a standard (RFC 8058) that lets mail clients unsubscribe a recipient with a single HTTPS POST, without opening a web page.
Check your own setup
Definitions help, but a real test is faster. Send an email to the free mail tester to see SPF, DKIM, DMARC and one-click unsubscribe results for your actual message, or paste your copy into the spam tester.
Frequently asked questions
What are SPF, DKIM and DMARC?
Three DNS-based email authentication standards. SPF lists the servers allowed to send for your domain, DKIM signs each message with a key published in DNS, and DMARC tells receivers what to do when neither passes in alignment with the From address.
What did Gmail and Yahoo change for senders in 2024?
Since February 2024, all senders must authenticate with SPF or DKIM. Bulk senders must also have SPF, DKIM and DMARC with an aligned From domain, support one-click unsubscribe (RFC 8058) on marketing mail, and keep the spam complaint rate below 0.3%.
Which email metrics matter most?
Spam complaint rate and hard bounce rate decide whether you keep reaching the inbox. Click-through rate is the most reliable engagement metric, because open rate is inflated by Apple Mail Privacy Protection.
Is this glossary tied to Lumail?
The definitions are vendor-neutral and cite the relevant RFCs and mailbox provider rules. Each entry ends with a short note on how Lumail handles the topic.
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