Email authentication & deliverability checks, programmatically

What it does

One call returns structured JSON across the checks Relaymetry already runs in production: SPF · DKIM · DMARC · MX · TLS (including MTA-STS and TLS-RPT) · blacklists. The same engine that powers the free tools and the monitoring dashboard — not a separate implementation.

What teams build with it

• Onboarding validationVerify a customer domain is correctly authenticated before you start sending on their behalf.
• Bulk auditsSweep a portfolio of client domains for SPF, DKIM, DMARC, and blacklist problems in one pass.
• Embedded health badgeShow a live email-health indicator for a domain inside your own dashboard or product.
• MonitoringPoll for record drift and blacklist appearances, and alert through your own pipeline.

How access works

During early access we provision keys individually — tell us your use case and expected volume, and the engineer who built the checker will reply personally. No self-serve signup yet, no credit card, no fake tier table.

What a check looks like

POST /api/v1/checks
Authorization: Bearer rlm_live_...

{
  "domain": "relaymetry.com",
  "checks": ["mx", "spf", "dkim", "dmarc", "tls", "blacklist"]
}

{
  "mx": {
    "status": "pass"
  },
  "spf": {
    "status": "pass"
  },
  "dkim": {
    "status": "warn",
    "detail": "No DKIM keys detected on the popular-selector list."
  },
  "dmarc": {
    "status": "pass"
  },
  "tls": {
    "status": "warn",
    "detail": "IPv6-only MX — TLS path not checked (IPv4 only)."
  },
  "blacklist": {
    "status": "pass"
  },
  "checkedAt": "2026-06-11T00:13:20.270Z"
}

Early access — the contract may evolve before general availability.

Authentication & limits

Requests authenticate with a Bearer API key (rlm_live_…). Per-key rate limits and quotas are tuned individually during early access — we'd rather size them to your real workload than publish numbers we'd have to walk back.

Request access

The form at the top of the page takes under a minute — tell us your use case and expected volume, and we'll reply personally.