Sending API, SMTP & developer experience
How this is scored
How an application sends mail: a REST API and an SMTP relay with their limits stated, official SDKs and drivers for named languages and frameworks (PHP and Laravel, Node, Python, Ruby and Rails, Java, Go, .NET), stored templates with variables and versions, batch sending, attachments, idempotency keys, scheduled sending, a test or sandbox mode that does not deliver, inbound email parsed into a webhook, and the quality of the API reference and guides.
0 — Not a sending service; an application cannot send email through it by API or SMTP.
3 — An API or SMTP credentials to send a message; SDKs, templates, limits and a test mode are basic or not described.
5 — A documented REST API and SMTP relay, official SDKs for several named languages, stored templates with variables, attachments and batch sending, rate limits stated, a sandbox or test mode, and quick-start guides for named frameworks.
8 — An API reference with every endpoint and error code, idempotency keys, scheduled sending, template versions and a template language documented, inbound email parsed to a webhook, an OpenAPI specification or official CLI, framework drivers maintained by the vendor, and a migration guide from named competitors.
10 — An API a team builds its product on: versioning and deprecation policy published, backward compatibility stated, full parity between API and SMTP features, local or staging test tooling that mirrors production, and every limit, timeout and retry behaviour documented.
The Agency Lead
A documented HTTPS API with one send endpoint and token authentication, an SMTP relay on port 587 with TLS required, official libraries for Node.js, Ruby, Python, PHP, Go and Elixir, and framework examples for Laravel, Django, Wordpress and Magento cover the essentials, and idempotency keys plus inbound email converted to JSON webhooks go further. For our per-client setups the domain API is genuinely useful — domains and per-domain API tokens can be provisioned over HTTP from an organisation token. The documentation states batch emails are not supported beyond 50 comma-separated recipients in the To field, and we found no public information on stored templates, rate limits, or a test or sandbox mode. 1 2 3 6 11 12