Brevo

API key authentication via api-key header. Keys are generated in the Brevo dashboard. Multiple keys can be created per account. No fine-grained scoping — keys grant full API access. SMTP credentials are separate from REST API keys for SMTP relay integration. No OAuth for third-party integrations (beyond partner integrations). For agents, creating a dedicated API key per integration is recommended. No key expiry. No IP restrictions on keys. The auth model is simple. For agents needing SMTP relay (Nodemailer, SMTP libraries), the SMTP credentials (username + password) provide a separate auth path. The main consideration: the api-key header name (not standard Authorization) requires custom header configuration.

Brevo (formerly Sendinblue) is a broad marketing platform covering transactional email, campaign email, SMS, WhatsApp, live chat, CRM, and marketing automation. For agents, the API covers transactional email sending (SMTP and REST API), contact list management, campaign creation and sending, SMS sending, and automation workflow management. The free tier (300 emails/day) is generous for development and small production use. The platform's breadth is both a strength and weakness: agents get multi-channel capabilities in one integration, but the API surface is large and some areas are less polished than specialized tools. For agents needing a cost-effective, multi-channel marketing platform with transactional email, Brevo is practical. The trade-off versus specialized tools: lower quality per-channel, broader capability per-integration.

REST API v3 at api.brevo.com/v3/. Transactional email: POST to /smtp/email with sender, to, subject, htmlContent or templateId. Contact management: POST /contacts for creation, GET /contacts/{identifier} for lookup, with custom attributes. Lists and segments for audience management. Campaign email: create, schedule, and send to lists/segments. SMS: POST to /transactionalSMS/sms. The API is organized by channel (SMTP, SMS, WhatsApp) and function (contacts, campaigns, automation). Template management enables reusable email designs. The API design is functional but shows its age in some areas — parameter naming is inconsistent across endpoints. Webhooks cover email delivery events (delivered, opened, clicked, bounced). Pagination uses limit/offset. Batch contact operations via CSV import.

API errors return JSON with code and message. Standard HTTP status codes. Rate limits: vary by plan and endpoint — transactional email has higher limits than campaign operations. The free tier's 300 emails/day limit is a hard cap. Bounce handling is automatic — bounced addresses are suppressed. Delivery reputation is shared on the free tier (shared IP) — agents should upgrade to dedicated IP for production volume. Webhook events for delivery, open, click, bounce, and unsubscribe provide delivery tracking. SMS delivery reports are available. The main reliability consideration: transactional email delivery speed depends on account reputation and sending volume. New accounts may experience slower delivery initially. For agents, monitoring delivery metrics and handling bounces/complaints is important for maintaining sender reputation.

Developer documentation at developers.brevo.com provides API reference, SDKs, and integration guides. The API reference is auto-generated with endpoint descriptions and parameter documentation. SDKs are available for PHP, Python, Node.js, Ruby, Go, Java, and C# — all official and maintained. The documentation covers email, SMS, WhatsApp, contacts, campaigns, and automation. Getting started guides are channel-specific. The documentation's main weakness: the breadth of the platform means navigating to relevant information requires familiarity with the product structure. Some endpoint descriptions are sparse. For agents, the transactional email API and contact management docs are the most important starting points. The Postman collection enables interactive API exploration.