Send email with Go

net/smtp is 1982

Go's net/smtp does exactly what the RFC says and nothing more: no HTML helpers, no auth beyond PLAIN and CRAM-MD5, and the package is frozen by design. The Go team themselves point users elsewhere.

Elsewhere is one stdlib HTTP call.

One POST, and the send is handled

body := `{"from":"[email protected]","to":"[email protected]",
  "subject":"Welcome","html":"<p>You're in.</p>"}`

req, _ := http.NewRequest("POST",
  "https://api.nitrosend.com/v1/my/messages",
  strings.NewReader(body))
req.Header.Set("Authorization", "Bearer "+os.Getenv("NITROSEND_API_KEY"))
http.DefaultClient.Do(req)

No third-party module, no SMTP dialer, no TLS negotiation to reason about. The response carries the message ID; your webhook carries the rest.

And the infrastructure behind that POST is sized like a systems engineer would want: we run on a million-a-day sending limit as a baseline, with five million a day available on request. Your Goroutines will not be the bottleneck, and neither will we.

The API design philosophy is fail-closed, which Go engineers will appreciate. We once found a misplaced scheduled_at field being silently dropped, which meant an immediate send instead of a scheduled one: a 24,000-email misfire waiting to happen. Now a wrong-shaped field fails closed with a 422 pointing at the correct one. Silent coercion is how footguns ship. The rule is a hardcoded invariant in the codebase now: audience resolution fails closed, never open.

Full parameters, responses, and error codes live in the REST API docs and the API reference.

import requests

requests.post(
  "https://api.nitrosend.com/v1/messages",
  headers={"Authorization": f"Bearer {KEY}"},
  json={"to": to, "subject": subj,
        "html": body})

{ "id": "msg_9f2c",
  "status": "accepted" }

And the part no library gives you

The same account exposes an MCP server, so the agent writing your code can also run your email. Point Claude, Cursor, or Codex at api.nitrosend.com/mcp and it composes, previews, and stages sends, with a human approving every one. The API is for your code. The MCP is for your agent. One platform either way.

Every send comes back with a message ID, and delivery events follow on your webhook: delivered, opened, bounced. No dashboard required to know what happened.

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