Send email with Rust

Skip the SMTP crates

lettre is solid if you genuinely need SMTP. But an SMTP crate brings TLS features, connection pools, and builder ceremony to a problem that, for most services, is one HTTP request with serde_json.

One POST, and the send is handled

reqwest::Client::new()
  .post("https://api.nitrosend.com/v1/my/messages")
  .bearer_auth(std::env::var("NITROSEND_API_KEY")?)
  .json(&serde_json::json!({
    "from": "[email protected]", "to": "[email protected]",
    "subject": "Welcome", "html": "<p>You're in.</p>"
  }))
  .send().await?;

The ? operator carries your error handling, the response deserializes into whatever type you define, and there is no mail server in your dependency tree.

The platform side moves at a pace Rust people will appreciate: one recent week shipped a rebuilt promptable email builder, five provider integrations, OAuth agent connect, and thirty-plus fixes from live sessions. Fast tools deserve fast infrastructure.

API keys are the server-side story here: a nskey_live_ key lives in your environment and authorizes the whole account, which is why it never belongs in client code. And the mail path behind that key is locked down the way a Rust reviewer would want. TCP 2525 is firewall-restricted to our API host, TLS and exact SMTP authentication are mandatory, every one-recipient route and MX snapshot is HMAC-signed, and unsigned or replayed requests are rejected outright.

A craft take Rust minimalists will like, from studying 47 of the best email designs of 2026: plain text outperforms 95 percent of HTML email, and restraint beats complexity every time. The same taste that trims your dependency tree ships better email.

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. If you are staying on SMTP, how to set up SMTP is the setup to follow, and SPF, DKIM and DMARC authentication is what stops those sends landing in spam.

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