Jargon Buster

Grow

Email & Deliverability

Sending email that actually arrives.

The territory

30 core terms mapped for this field, ranked by how often builders reach for them. Each one is a future entry. Want to bust one? One entry, one file, one pull request.

  • SPFDNS record listing servers allowed to send for your domain"the DNS thing that says who can send email as me" · "proving my server is allowed"
  • DKIMCryptographic signature proving an email wasn't forged or altered"the signature key thing for email" · "signing my emails so they look legit"
  • DMARCPolicy telling inboxes what to do when SPF/DKIM fail"the rule that stops people spoofing my domain" · "the p=reject thing"
  • DMARC identifier alignmentVisible From domain matching authenticated SPF/DKIM domain"domain alignment" · "making the from address match the signed domain"
  • Sender reputationScore mailbox providers assign your domain/IP based on behavior"my email credit score" · "whether Gmail trusts me"
  • Domain warmingGradually ramping send volume to build sender reputation"starting slow so I don't get flagged" · "breaking in a new sending domain"
  • Transactional emailOne-to-one triggered mail: receipts, resets, confirmations"the automatic emails the app sends" · "receipt and password reset mail"
  • Bulk email and marketing emailBroadcast mail to lists, subject to stricter consent rules"newsletter blasts" · "campaign email"
  • Hard bouncePermanent delivery failure; address is invalid or dead"the address doesn't exist" · "permanently undeliverable"
  • Soft bounceTemporary failure: full mailbox, server down, throttled"bounced but might work later" · "temporary reject"
  • Spam complaint ratePercent of recipients hitting "report spam"; keep under 0.3%"how many people mark me as junk" · "the complaint threshold"
  • Complaint feedback loop (FBL)Provider-sent report when a recipient marks you spam"getting told who reported me" · "the complaint feed from Gmail/Yahoo"
  • Suppression listAddresses you must never send to again"the do-not-send list" · "blocklist of my own unsubscribes"
  • List hygieneRemoving dead, bouncing, and inactive addresses regularly"cleaning my list" · "pruning dead emails"
  • Double opt-inSubscriber confirms via emailed link before receiving mail"make them click a confirm link" · "confirmed signup"
  • One-click unsubscribeRequired header letting inboxes unsubscribe without a page"the unsubscribe button Gmail shows at the top" · "List-Unsubscribe-Post"
  • Inbox placement vs delivery rateAccepted by server versus actually landing in Inbox"it says delivered but went to spam" · "where it actually lands"
  • Blocklist (RBL/DNSBL)Public lists of IPs/domains inboxes refuse or filter"getting blacklisted" · "Spamhaus listing"
  • Spam trapDead or planted address used to catch sloppy senders"the honeypot address that gets me flagged" · "poisoned email in my list"
  • Envelope vs header FromBounce address versus the address recipients see"the From you see versus the real sender" · "MAIL FROM vs the visible From"
  • Custom MAIL FROM domain (branded Return-Path)Your own bounce-handling domain, aligning SPF"custom return-path" · "the hidden bounce address"
  • Subdomain sendingIsolating mail streams on subdomains to protect the root domain"send from mail.mysite.com" · "keeping marketing off my main domain"
  • DMARC aggregate report (RUA)Daily XML report on who's sending as your domain"the DMARC report emails I keep getting" · "the daily XML from Gmail"
  • Email delivery event webhooksProvider callbacks for delivered, bounced, opened, complained"webhook events" · "callbacks when my mail bounces"
  • Engagement signalsOpens, replies, moves-to-inbox that providers use to rank you"whether people actually read it" · "the signals Gmail watches"
  • Throttling / rate limitingProviders capping how fast you may deliver"sending too fast and getting deferred" · "4xx slow-down"
  • SMTP deferral and greylistingTemporary rejection expecting a legitimate retry"rejected then accepted on retry" · "the wait-and-try-again reject"
  • Postmaster tools / domain reputation dashboardProvider-side view of your spam rate and reputation"Google Postmaster Tools" · "the dashboard showing my spam rate"
  • Sunset policyAutomatically stopping mail to long-inactive subscribers"cutting off people who never open" · "retiring dead subscribers"
  • Email service provider and SMTP relayCampaign platform versus raw programmatic sending API"the thing that actually sends my mail" · "API vs newsletter tool"

Deeper in the field

  • MX record DNS entry naming the server that receives your domain's mail
  • Reverse DNS (PTR) Maps a sending IP to its mail server hostname
  • DKIM selector Identifies the public key used to verify a DKIM signature
  • DKIM key rotation Replaces signing keys periodically without interrupting authentication
  • Authentication-Results header Shows receiver-evaluated SPF, DKIM, and DMARC outcomes
  • ARC (Authenticated Received Chain) Preserves auth results across forwarding hops
  • Reply-To Header routing replies somewhere other than the sender address
  • Message-ID / References headers Threading identifiers grouping replies in inboxes
  • List-Unsubscribe header Advertises supported unsubscribe methods to mailbox clients
  • SMTP reply codes Distinguish acceptance, temporary deferral, and permanent rejection
  • Retry queue Retains deferred messages and retries them with controlled backoff
  • Bounce processing Classifies failures and suppresses permanently undeliverable recipients
  • Bounce rate Percentage of attempted messages rejected by receiving servers
  • Email address validation Screens malformed, disposable, or risky addresses before sending
  • IP warming Gradually increases volume on a new dedicated sending IP
  • Dedicated vs shared IP Sending from your own IP versus a pooled one
  • Seed list testing Sending to test accounts across providers to check placement
  • Gmail tab classification Gmail sorting mail into Primary, Promotions, Updates
  • Link tracking domain Branded redirect domain for click tracking, avoids shared-domain taint
  • Multipart/alternative email Text alternative bundled with HTML for filters and clients
  • Content-based spam filtering Filters rating wording, links, and formatting risk