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@lacspace/email-lint

v1.0.0Mail Kit0 deps

Pre-send email linter for webmail and campaign tools: tells you in plain English what will hurt deliverability or render badly before you hit send. 41 stable rules covering Gmail clipping (~102KB), risky and oversized attachments, image-only mail, missing alt text, link-text/href domain mismatch, URL shorteners, IP and javascript: links, spammy subjects and phrases (English + Nepali), ALL CAPS, hidden text, scripts, external stylesheets, Outlook-unsupported CSS, forms, embeds, inline SVG, base64 images, malformed HTML, and Gmail/Yahoo bulk-sender rules (List-Unsubscribe, RFC 8058 one-click). Returns a 0-100 score, good/fair/poor grade, issues with fixes, and stats. Nepali messages for the key rules. Heuristic; does not render. Zero dependencies, isomorphic, tolerant HTML tokenizer built in.

npm i @lacspace/email-lint
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Usage

email-lint.ts
import { lintEmail } from "@lacspace/email-lint";

const result = lintEmail(
  {
    subject: "Your October product update",
    preheader: "Faster search, calmer inbox, new shortcuts.",
    from: "Lacspace <news@lacspace.com>",
    html: campaignHtml,
    text: campaignText,
    headers: {
      "List-Unsubscribe": "<https://lacspace.com/u/abc>, <mailto:unsub@lacspace.com>",
      "List-Unsubscribe-Post": "List-Unsubscribe=One-Click",
    },
    bulk: true,
  },
  { rules: { "links.http_insecure": "off" } },
);

result.score;  // 92
result.grade;  // "good"
result.issues; // [{ id: "images.missing_alt", severity: "warn", count: 1,
               //    message: "1 image has no alt text, so readers with images off ...",
               //    fix: "Add an alt attribute describing each image. ..." }]
result.stats;  // { sizeBytes, imageCount, linkCount, textToImageRatio, textChars, wordCount }

Exports 5

RULESSPAM_PHRASESlintlintEmailspamPhrases

Keywords

emailemail-lintdeliverabilityspamspam-scorepre-send

More in Mail Kit

@lacspace/email-templates

Compose bulletproof, responsive, dark-mode HTML emails from simple blocks, plus 13 ready-made transactional templates (OTP, verify, password-reset, magic-link, receipt, order, shipping, invitation, digest, announcement). Ships plaintext generation, preheaders and {{var}} i18n interpolation. Zero-dependency, isomorphic.

@lacspace/email-validate

Smart, network-free email validation — RFC-5322 syntax (incl. quoted local parts & IP-literal domains), disposable/temp-mail & role-account detection, free-provider flags, Gmail normalization and 'did you mean?' typo suggestions. Zero-dependency, isomorphic.

@lacspace/email-verify

Best-effort email deliverability for Node — syntax + disposable/role, MX lookup with priority ranking, an optional SMTP RCPT probe (no mail sent), catch-all detection, a 0-100 confidence score, and de-duped batch verification. All DNS/SMTP injectable; zero npm dependencies.

@lacspace/mailer

A tiny zero-dependency SMTP client for Node — send email over raw net/tls with STARTTLS & AUTH, plus a fluent MIME builder (inline images, attachments, alternatives), RFC 5322 address + RFC 2047 helpers, batch send with retry, and no-network test transports. Provider presets (Hostinger, Gmail, Outlook, Zoho…) make setup one line.

@lacspace/imap

Zero-dependency IMAP4rev1 client for Node (RFC 3501 + IDLE, MOVE, UIDPLUS, CONDSTORE, SPECIAL-USE, LIST-EXTENDED, LITERAL+, SASL-IR, QUOTA, ID). Implicit TLS and STARTTLS with verification on, LOGIN / PLAIN / XOAUTH2 / OAUTHBEARER, streaming byte-accurate parser, async-iterable FETCH, envelopes with RFC 2047 decoding, BODYSTRUCTURE trees shared with @lacspace/mime, modified UTF-7 mailbox names, special-use detection (incl. Gmail XLIST and localised names), IDLE with NOOP fallback. Works with Hostinger (Dovecot), Gmail, Outlook/Exchange, GoDaddy.

@lacspace/mime

Isomorphic RFC 5322 / RFC 2045-2049 MIME parser and builder for webmail. parseMime() turns raw mail (string or bytes) into from/to/cc/subject/date/text/html/attachments/inline cid images/priority/List-Unsubscribe one-click and the part tree; handles nested multipart (mixed, alternative, related, report, signed), message/rfc822 forwards, base64 and quoted-printable (tolerant), RFC 2047 encoded words (split multibyte, adjacent whitespace), RFC 2231 parameters, 30+ charsets and malformed input without ever throwing. parseBodyStructure() parses IMAP BODYSTRUCTURE (literals, extension data) into the same tree with IMAP partIds, plus findTextParts / listAttachments / decodePart for lazy fetching. buildMime() writes CRLF messages with encoded-word headers, QP/base64 bodies, mixed/alternative/related nesting, Message-ID generation and header-injection guards; replyHeaders() / forwardSubject() for threading. Pairs with @lacspace/imap and @lacspace/mailer. Zero dependencies; Node 18+, edge runtimes and browsers.

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