The whole stack — IPs, MTAs, signing, signals.

Most "email APIs" you've used were a thin wrapper around someone else's deliverability problem. Relayly runs the actual MTAs, owns the IPs, signs the headers, and gives you the live signals you need to ship without surprises.

Sending

Multi-region MTAs, one API call

We run our own outbound mail-transfer agents in EU (Gravelines, FR) and Canada (BHS, QC). Pick a region per send for compliance or latency, or let us auto-route from the recipient's locale.

  • EU + CA egress today, US planned
  • Per-recipient region pinning for healthcare / GDPR
  • Active failover — if one region degrades, we drain to the other in <30 seconds
  • Direct rDNS — every IP resolves to a relayly subdomain that aligns with HELO + DKIM
# pin to EU POST /v1/email/send { "region": "eu", "to": [{"email":"u@example.com"}], "subject": "Hello", "html": "<p>Hi</p>" } # or recipient-locale auto { "region": "auto" }
Authentication

Per-domain DKIM. No shared keys.

Every domain you verify gets a private 2048-bit RSA key generated in your account. We never share it across customers and never rotate without you triggering it. SPF, DKIM, and DMARC records are auto-suggested in the dashboard with copy-paste-ready values.

  • Per-account, per-domain DKIM private keys
  • Optional ED25519 signing for modern servers
  • Inline DNS validator — clicks the green check the moment your records propagate
  • Custom Return-Path domain for stronger DMARC alignment
SPF DKIM esp1 DMARC MTA-STS TLS-RPT BIMI
All six DNS records auto-generated, validated, and watched for drift.
Deliverability brain

Provider-aware routing

Gmail, Office 365, Yahoo, and Proofpoint each have their own quirks — and their own reputation tracks. Our worker classifies the recipient's MX, looks up your last 24h success at that provider, and picks the IP × domain pair most likely to land in the inbox.

  • Mailbox-provider classifier (10+ providers, auto-updated)
  • Reputation scored per (IP × domain × provider) tuple
  • Auto-routing around throttled or 421-deferring IPs
  • Manual pin available for pinned-IP customers
ProviderBest IP24h delivered
Gmailmta-2 / mkt99.4%
O365mta-can-1 / tx98.7%
Yahoomta-3 / news97.2%
Proofpointmta-can-1 / tx96.9%
Reputation engine

Real IP warmup. Not a knob.

New dedicated IPs start at 50 sends/day and ramp on a 14-day curve based on actual delivery success at each major provider. If Gmail starts deferring, we tighten the cap for Gmail specifically — not globally — so the rest of your traffic keeps flowing.

  • 14-day default warmup curve, override per IP
  • Per-provider cap — Gmail trouble doesn't throttle Yahoo
  • Auto-pause on consecutive 5xx spikes, with alert
  • Live curve visible in Deliverability → IP pools
# Day 1 cap = 50 delivered = 48 ✓ # Day 4 cap = 800 delivered = 792 ✓ # Day 8 cap = 5000 delivered = 4965 ✓ # Day 14 cap = 25000 delivered = 24913 ✓ # → Gmail throttle detected cap[gmail] = 10000 (auto)
Webhooks & signals

HMAC-signed events, replay-safe

Every delivered, bounced, opened, clicked event is HMAC-SHA256 signed with a per-endpoint secret you rotate from the dashboard. Verify in 6 lines. Replay attacks defeated by a 5-minute timestamp window.

  • 9 event types, all signed
  • Per-endpoint secret rotation
  • 24-hour exponential-backoff retries on non-2xx
  • Full delivery log + manual replay UI
POST /your/webhook HTTP/1.1 X-Relayly-Signature: t=1714672000,v1=a8c3… Content-Type: application/json { "event": "email.delivered", "message_id": "01HVQ8K7…", "timestamp": 1714672000, "to": "user@example.com" }
Marketing tier

Contacts, lists, segments, automations

Opt-in transactional, but we also speak the marketing dialect when you need it: contact lists, predicate-based segments, drag-and-drop visual flows, double opt-in signup forms, and one-click List-Unsubscribe per RFC 8058 baked into every send.

  • Predicate-based segments — opened in last 30d, joined within 14d, custom field equals X
  • Visual flow builder — wait, branch, send, tag
  • RFC 8058 List-Unsubscribe-Post (Gmail / Yahoo bulk-sender requirement)
  • A/B variant runner with statistical winner picker
  • Drag-and-drop email designer (MJML under the hood)
Contacts Lists Segments Templates Campaigns Flows Forms Suppressions
If you've used Klaviyo or Mailchimp, the model will feel familiar — but with the deliverability stack of an infrastructure ESP.
Compliance & security

Built like a service that holds PII

  • SOC 2 Type II program (audit underway, Q3 target)
  • GDPR Article 28 DPA available on signup, EU sub-processor list public
  • Self-serve "right-to-erase" — DELETE /v1/contacts/{email} purges from all systems
  • HIPAA BAA on Enterprise tier on request
  • SSO (SAML 2.0 + OIDC), SCIM 2.0 user provisioning, RBAC roles, audit log
  • Two-factor authentication (TOTP) and password-reset flow audited Phase 0
SOC 2 (in progress) GDPR HIPAA BAA DPA SAML OIDC SCIM RBAC
Read the Security page →
Integrations

Two ways in: REST or SMTP

Your stack already has whatever-it-is. We meet it. SMTP relay on port 587 for legacy code; REST + OpenAPI 3.1 spec + SDKs in 6 languages for everything new.

  • SMTP relay — point any client at smtp.relayly.io:587
  • REST API with OpenAPI 3.1 spec and Postman collection
  • SDKs: Node, Python, Go, Ruby, PHP, Java
  • FreshSales, HubSpot, Segment, Zapier connectors (beta)
# Either path — same backend SMTP smtp.relayly.io:587 REST https://api.relayly.io/v1 # Same per-message metadata X-Relayly-Tags: signup,welcome X-Relayly-Idempotency-Key: "abc-123"

See it for yourself in 10 minutes

No sales call. No contact-us-for-pricing. Just sign up, verify a domain, send.

Start sending free Read the docs