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Email Address Validation (Pre-Send Gate)

Email Address Validation (pre-send gate)

Owner: CodeCraft (tooling) Implemented: 2026-04-18 (after Quran outreach 2-bounce incident) Script: ~/system/tools/email-address-validate.js Cache: ~/system/databases/email-address-cache.sqlite (7-day TTL)

Why

First-send to uncatalogued institutional addresses (Al-Burhan, FIN Sarajevo) bounced because of typo/wrong-user assumptions. Adding an MX-lookup gate in front of SMTP send catches that class of failure before a message leaves the building.

What it does

Layer Catches Cost
Syntax check (RFC 5322 simplified) invalid@ or missing domain negligible
DNS MX lookup Nonexistent domain, missing MX records ~50–200 ms first time, cached after
SMTP RCPT probe (optional, --probe) Hard 550 rejections on strict servers ~1–5 s
Cache Repeat validation on known addresses 0 ms

What it does NOT catch

Gmail-hosted domains respond 250 accepted to RCPT even for nonexistent recipients. The real NDR arrives seconds/minutes later from the submission pipeline. Since many academic/institutional domains are on Google Workspace, RCPT probing is not a reliable filter for the class of errors we hit.

Mitigation: the validator prints a WARN when sending to a first-seen Gmail-hosted address, instructing the caller to verify manually.

Integration

mail-native.js sendEmail() calls the validator before the Himalaya/SMTP path. Hard-block on exit=1 (no MX / syntax). --force bypasses.

CLI

node ~/system/tools/email-address-validate.js <email>          # syntax + MX, cached
node ~/system/tools/email-address-validate.js <email> --probe  # + SMTP RCPT (see caveat above)
node ~/system/tools/email-address-validate.js <email> --force  # skip cache

Exit codes: 0 valid, 1 invalid, 2 transient/unknown.

  • ~/system/docs/quran-research/ — the outbound sprint that exposed the gap.
  • ~/system/tools/email-safety.js — existing content/subject gates.

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