Brevo

Brevo (formerly Sendinblue) bundles transactional, marketing, CRM, and SMS. The 300-emails-per-day free tier is one of the most generous in the market. Best as an all-in-one for small businesses; pure-API users may find the surface broader than they need.

An agent stack treats email as a two-way primitive. Inbound has to arrive as structured JSON a tool call can consume, sends have to be safe to retry when a model loop repeats itself, and every action needs an audit trail. A provider without inbound parsing only solves half the problem.

Against inbound parsing into tool calls and model-generated sends that must not duplicate, Brevo covers inbound parsing, webhook coverage, event stream, batch sending, and SDK breadth, and does not cover idempotency keys, operating track record, and multi-tenant support. Whether that gap matters depends on how central those are to the build.

• Inbound parsing: Yes
• Idempotency keys: No
• Webhooks: Yes
• Operating since: 2012
• Event stream: Yes
• Best published rate per 1,000: Tiers not published in comparable form
• Batch sending: Yes
• SDKs: node, python, go, ruby, php, java, dotnet
• Multi-tenant: No

Reliable for marketing and transactional; per-day free-tier limits prevent spam abuse.

Small businesses that need email plus marketing plus SMS in one place.