A security review can stall an email integration for weeks. The reviewer wants to know exactly which mailboxes your app can touch, how you prove a webhook came from the API and not an attacker, where the data lives, and how a customer cuts off access the day they offboard. Answer those questions with vague assurances and the deal slips a quarter.
This page maps each of those requirements to a concrete primitive you can point a security team at: scoped OAuth through /v3/connect/auth, revocable grants, HMAC-signed webhooks, encryption in transit and at rest, and the data-residency choice between the US and EU regions. Where a compliance posture depends on your own Nylas plan and contract, this says so plainly instead of overpromising.
What does a secure email API need for enterprise compliance?
Section titled “What does a secure email API need for enterprise compliance?”A secure email API needs five controls a reviewer will ask about by name: scoped OAuth so the integration requests only the permissions it uses, revocable access so a customer can sever the connection on demand, signed webhooks so forged events can’t reach your handler, TLS in transit with encryption at rest, and a documented data-residency region. Each maps to a verifiable endpoint or setting below.
The API handles the provider-side OAuth dance for Google, Microsoft, Yahoo, iCloud, IMAP, and Exchange behind one flow, so you implement these controls once instead of per provider. That matters when a security questionnaire asks the same six questions for every mailbox source. A single connector and one signing model covers all of them, which collapses a multi-week per-provider review into one conversation. The table later in this page lines up each requirement against the primitive that satisfies it.
How do I ensure email integration security across multiple enterprise customers?
Section titled “How do I ensure email integration security across multiple enterprise customers?”Isolate every customer behind a grant, the per-account credential the API issues after OAuth. Each grant carries its own token to a single mailbox, so one customer’s grant can never read another’s inbox, and GET /v3/grants lists exactly which accounts your application can reach. When a customer offboards, you delete their grant alone and the other connections stay live.
Multi-tenant email integration fails when one leaked token exposes every customer, so the boundary has to sit at the account, not the application. A grant is that boundary: requests run as /v3/grants/{grant_id}/messages, and the grant_id scopes the call to one mailbox. Store each grant_id against your own tenant record, never in client-side code. For the storage pattern, the store OAuth credentials securely guide covers encrypting tokens at rest and keeping the grant_id out of logs. To fully offboard a customer, delete the grant with DELETE /v3/grants/{grant_id}; to invalidate active tokens without removing the connection, POST /v3/connect/revoke revokes the access token and all child tokens in one call.
curl --request GET \ --url 'https://api.us.nylas.com/v3/grants?limit=50' \ --header 'Authorization: Bearer <NYLAS_API_KEY>'What are the best practices for enterprise-grade email authentication?
Section titled “What are the best practices for enterprise-grade email authentication?”Enterprise-grade email authentication means OAuth 2.0 with the narrowest scopes the integration needs, no stored passwords, and a clean revocation path. Microsoft deprecated basic authentication for all Exchange Online accounts on October 1, 2022, so OAuth is the only supported path for Microsoft 365 anyway. Request read-only scopes when you only read mail, and add write scopes solely when you send.
The hosted auth flow starts at GET /v3/connect/auth, where you pass a provider, a redirect_uri, and the OAuth scopes the integration requires. Requesting Mail.Read instead of full mailbox access is the single change that most often clears a least-privilege review, because the consent screen the customer sees lists only what you asked for. The hosted OAuth documentation details the authorization code flow and optional PKCE for client-side apps. Build the authorization URL, then redirect the user to it.
curl --request GET \ --url 'https://api.us.nylas.com/v3/connect/auth?client_id=<NYLAS_CLIENT_ID>&redirect_uri=https%3A%2F%2Fyourapp.com%2Fcallback&response_type=code&provider=google'Encryption in transit and at rest
Section titled “Encryption in transit and at rest”Every request to the API travels over TLS, and the base URL https://api.us.nylas.com rejects plain HTTP, so credentials and message bodies are never exposed on the wire. Webhook destinations must also use an HTTPS webhook_url, which encrypts both the notification body and its signature in transit. At rest, stored mailbox data and tokens are encrypted on the platform side.
Transport encryption only protects data while it moves, so the at-rest side matters just as much for a compliance review. On your end, encrypt the tokens you persist and never write a grant_id or access token to application logs, where a 30-day log retention window can quietly extend a token’s blast radius. Confirm the current at-rest encryption and key-management details for your plan with your Nylas account team, since the exact guarantees depend on your contract rather than a single fixed setting.
Audit logging and proving event authenticity
Section titled “Audit logging and proving event authenticity”The API signs every webhook with an HMAC-SHA256 digest in the x-nylas-signature header, a 64-character hex string computed from the raw request body using a webhook_secret only your endpoint and the platform share. Recompute it and compare in constant time, and a forged message.created never reaches your business logic. That signature is your tamper-evidence for inbound events.
For an audit trail a reviewer accepts, log the verification result, not the payload, and never the secret. Rotate the secret through POST /v3/webhooks/rotate-secret/{id} if it leaks. The full constant-time check, including the gzip-body gotcha that breaks most first attempts, lives in the verify webhook signatures guide. Pair signing with HTTPS and a source-address allowlist for defense in depth, and you can show a clear chain from event received to event trusted.
Data residency and SOC 2 / HIPAA posture
Section titled “Data residency and SOC 2 / HIPAA posture”The API offers two data regions: the US region at https://api.us.nylas.com and the EU region at https://api.eu.nylas.com. Choosing the EU region keeps connected mailbox data inside the EU, which answers the data-residency question many enterprise and public-sector buyers raise first. You pick the region when you create your application, and the base URL in every request reflects that choice.
SOC 2 and HIPAA posture depends on your specific plan and a signed agreement, so treat any blanket claim with skepticism. The honest answer for a buyer: confirm the current certification scope and request a SOC 2 report or a Business Associate Agreement directly through your account team, then map the controls on this page to your own requirements. The Nylas Trust Center publishes the current security and compliance program. Don’t repeat a compliance claim you can’t back with a document the customer can read.
Security primitive to requirement map
Section titled “Security primitive to requirement map”This table lines up each enterprise requirement with the verified primitive that satisfies it, so you can hand a reviewer a single reference instead of stitching answers together across six provider integrations. The unified column is the path you implement once and reuse across Google, Microsoft, Yahoo, iCloud, IMAP, and Exchange.
| Requirement | Build it yourself, per provider | Unified Nylas primitive |
|---|---|---|
| Scoped access | Per-provider OAuth apps and scope mapping | /v3/connect/auth with requested scopes |
| Revocable access | Provider-specific token revocation calls | /v3/connect/revoke and per-grant deletion |
| Event authenticity | Custom signing per webhook source | HMAC-SHA256 x-nylas-signature |
| Tenant isolation | Map tokens to tenants by hand | One grant_id per customer mailbox |
| Data residency | Self-host per region | US or EU region base URL |
The build-it-yourself column isn’t wrong for every team. If you support one provider and one region and want full control of token storage and key rotation, calling Gmail API or Microsoft Graph directly removes a dependency. The tradeoff shows the moment you add a second provider: you repeat the OAuth app, the scope review, and the signing model from scratch, and your security questionnaire doubles.
What’s next
Section titled “What’s next”- Store OAuth credentials securely for encrypting tokens and keeping the
grant_idout of logs - List and revoke grants to audit and sever customer access on demand
- Verify webhook signatures for the constant-time HMAC check and the gzip body gotcha
- Getting started with Nylas to create a project, connector, and your first scoped grant