curl -X POST https://smtpfa.st/api/v1/emails \
  -H "Authorization: Bearer $SMTPFAST_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "hello@yourapp.com",
    "to": ["user@example.com"],
    "subject": "Welcome!",
    "html": "<h1>Hello!</h1>"
  }'

Or from a terminal with the CLI:

npx smtpfast login
npx smtpfast send --from hello@yourapp.com --to user@example.com --subject "Welcome!" --text "Hello!"

Create an API key and verify your sending domain in the dashboard. Already on Resend? Point your code at https://smtpfa.st/api/v1 and swap the key. See the migration guide.

• smtpfast-cli: every API endpoint as a command, generated from the OpenAPI spec and released automatically when the API changes. npm install -g smtpfast, or a single binary for macOS, Linux and Windows.
• terraform-provider-smtpfast: manage sending domains, API keys and webhooks as code. On the Terraform Registry.
• smtpfast-skill: an Agent Skill that teaches Claude and other agents to use the SMTPfast API.
• feedletter: turn an RSS feed or a folder of Markdown into a newsletter, curated in a browser studio and sent with SMTPfast.

• Resend-compatible API for emails, templates, inboxes, contacts, segments and webhooks, so Resend SDKs and existing code keep working. The full OpenAPI spec is public.
• Hosted templates with variables, a live desktop, mobile and dark-mode preview, and ten starters.
• Inboxes on your own domain: received mail in threads, with labels, folders, and drafts that a person approves before an agent's reply goes out.
• Built for agents: a hosted MCP server with OAuth covers almost the whole API. Agents never get to create API keys or change team members.
• Deliverability built in: DKIM, SPF and DMARC setup, one-click DNS on Cloudflare, suppressions, and live delivery logs.
• Teams with roles, and broadcasts, signup forms and transactional email in one place.