Glossary

The words, defined properly.

Deliverability, consent, platform and measurement vocabulary — written for operators rather than for a search engine. Every entry says what the thing is, why it matters, and where it shows up in practice.

Browse A–Z →Read the guides
12 terms · 6 deliverability · 3 compliance · 2 platform · 1 measurement
C
DeliverabilityComplaint rateSpam rate · Abuse rateComplaint rate is the proportion of delivered messages that recipients mark as spam, and it is weighted more heavily by mailbox providers than any other single sender signal.ComplianceConsent evidenceProof of consent · Consent recordConsent evidence is the retained record proving how, when, and on what lawful basis a person agreed to receive email — as opposed to a flag merely asserting that they did.
D
DeliverabilityDKIMDomainKeys Identified MailDKIM adds a cryptographic signature to outgoing email, letting receiving providers verify — using a public key in your DNS — that the message was authorised by your domain and has not been altered in transit.DeliverabilityDMARCDomain-based Message Authentication, Reporting and ConformanceDMARC is a DNS policy that tells receiving mailbox providers how to handle mail claiming to be from your domain when it fails both SPF and DKIM alignment — and where to send reports about those failures.ComplianceDouble opt-inConfirmed opt-in · DOIDouble opt-in is a signup flow where the subscriber must confirm their address — usually by clicking a link in a confirmation email — before any marketing is sent to it.
F
PlatformFrequency capSend limit · Fatigue capA frequency cap limits how many messages a single contact can receive within a rolling time window, enforced across campaigns and automations alike rather than per send.
H
DeliverabilityHard bouncePermanent failureA hard bounce is a permanent delivery failure, usually meaning the recipient address does not exist or the receiving domain refuses mail for it outright.
M
PlatformMessage classMarketing vs transactionalMessage class marks a send as marketing or transactional, determining whether topic consent and frequency caps apply to it and which provider routes carry it.
O
MeasurementOpen rateUnique open rateOpen rate is the proportion of delivered emails recorded as opened, measured by a tracking pixel — a metric now substantially inflated by privacy features and best treated as a trend indicator rather than a fact.
S
DeliverabilitySoft bounceTemporary failure · 4xxA soft bounce is a temporary delivery failure, such as a full mailbox or an unavailable server, where retrying later is appropriate rather than suppressing the address.DeliverabilitySPFSender Policy FrameworkSPF is a DNS TXT record that lists the mail servers authorised to send on behalf of your domain, letting receiving providers reject mail from anywhere else.ComplianceSuppression listDo-not-send list · Exclusion listA suppression list is the retained record of addresses that must not be sent to, along with the reason and scope of each block, kept as evidence rather than deleted.

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