Email verification and deliverability, defined
Short, accurate definitions of the terms you meet when you verify lists, find work emails and send cold outreach, from catch-all domains to DMARC.
B
- B2B dataB2B data is information about businesses and the people who work there, such as company details, job titles and work emails, used for sales and marketing.
- BIMIBIMI lets a domain show its brand logo next to authenticated emails in supporting inboxes. It requires DMARC at enforcement and an SVG logo.
- BlocklistA blocklist (blacklist, DNSBL) is a list of IP addresses or domains linked to spam, which mail servers query in DNS to reject or filter mail.
- Bounce rateBounce rate is the share of sent emails returned as undeliverable: bounced messages divided by messages sent, usually split into hard and soft bounces.
C
- Catch-all domainA catch-all domain's mail server accepts email for any address at that domain, so a verifier can't confirm whether a specific mailbox exists.
- Cold emailA cold email is a first, unsolicited business email to someone with no prior relationship with the sender, usually for sales, hiring or partnerships.
D
- Data controller vs data processorUnder GDPR, a controller decides why and how personal data is processed; a processor processes it on the controller's behalf and instructions.
- Disposable emailA disposable email is a temporary address from a throwaway inbox service, used to sign up without giving a real address. It often stops working soon after.
- DKIMDKIM adds a cryptographic signature to each email; receivers verify it with a public key published in DNS at selector._domainkey.domain.
- DMARCDMARC needs SPF or DKIM to pass and align with the From domain, and tells receivers what to do with failing mail: none, quarantine or reject.
- Domain reputationDomain reputation is how mailbox providers rate a sending domain based on the mail sent under it, independent of the IP addresses used.
- Double opt-inDouble opt-in means a new subscriber confirms their address by clicking a link in a confirmation email before they're added to a mailing list.
E
- Email deliverabilityEmail deliverability is the ability to get emails into the inbox rather than bounced or sent to spam. It depends on lists, authentication and reputation.
- Email finderAn email finder takes a person's name and company and returns their most likely work email address, ideally verified before it's returned.
- Email formatAn email format is the pattern a company uses to build employee addresses from their names, such as [email protected] or [email protected].
- Email permutationEmail permutation means generating likely address variations from a name and company domain, such as jane.doe@, jdoe@ and janed@, then testing them.
- Email syntaxEmail syntax is the set of rules for a well-formed address: a local part, an @ sign and a domain, as defined in RFC 5322 with length limits from RFC 5321.
- Email validationEmail validation checks that an address is correctly formed and its domain can take mail. The term is often used interchangeably with email verification.
- Email verificationEmail verification checks if an address can receive mail: syntax, domain, MX records and a mailbox check with the mail server, without sending an email.
- Email warm-upEmail warm-up is gradually increasing sending volume from a new domain, mailbox or IP so mailbox providers can build a reputation for it.
L
- Lead enrichmentLead enrichment adds missing details to existing lead records, such as a verified work email, job title or company data, so they're usable for outreach.
- Legitimate interest (GDPR)Legitimate interest is a GDPR lawful basis (Article 6(1)(f)) for processing necessary for your interests, unless outweighed by the person's rights.
- List hygieneList hygiene is the routine of removing invalid, unsubscribed and unengaged addresses from a list so you only email people who can and should get mail.
M
- Mailbox providerA mailbox provider hosts inboxes and decides what reaches them, for example Gmail and Google Workspace, Outlook.com and Microsoft 365, or Yahoo.
- MX recordAn MX record is a DNS record naming the mail servers that accept email for a domain, each with a preference number. Lower numbers are tried first.
S
- Sender reputationSender reputation is how mailbox providers judge your trustworthiness as a sender, based on your IPs, domains, complaints, bounces and engagement.
- SMTPSMTP (Simple Mail Transfer Protocol) is the standard protocol mail servers use to send and relay email across the internet, defined in RFC 5321.
- SMTP response codesSMTP response codes are three-digit replies from a mail server: 2xx means success, 4xx a temporary failure to retry, and 5xx a permanent failure.
- Soft bounceA soft bounce is a temporary delivery failure, signalled by a 4xx SMTP reply, such as a full mailbox, a busy server, rate limiting or greylisting.
- Spam complaint rateSpam complaint rate is the share of delivered emails that recipients mark as spam. Feedback loops report those complaints back to the sender.
- Spam trapA spam trap is an email address used to catch senders with poor list practices. It never opted in, so any mail it receives counts against the sender.
- SPFSPF (Sender Policy Framework) is a DNS TXT record listing the servers allowed to send mail for a domain, checked against the envelope MAIL FROM domain.
- Suppression listA suppression list (do-not-contact list) holds addresses and domains you must never email, such as unsubscribes, complaints and hard bounces.
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