One HTTPS endpoint for sending email, and a webhook for what happens next. There are official libraries for eight languages, and every example on this page is also written out as a plain HTTP request, so anything that can reach the internet can use it.

Base URL

https://api.densend.com/v1

Auth

Bearer token in the Authorization header

Format

JSON in, JSON out

Sending domain

Must be verified before you can send from it

1. 1Add and verify a domain under Domains. Publish the DNS records it gives you and it verifies itself, usually within a minute.
2. 2Create an API key under API Keys. It is shown once, so copy it then.
3. 3Install the package for your language, then send your first email with the call below. Switch language with the tabs.

import { DenSend } from "@densend/node";

const densend = new DenSend(process.env.DENSEND_API_KEY);

const { id } = await densend.emails.send({
  from: "You <[email protected]>",
  to: "[email protected]",
  subject: "Hello from DenSend",
  html: "<p>Your order has shipped.</p>",
});

console.log(id);

A successful send returns 202 with the id of each message created. One id per recipient, because a bounce belongs to exactly one address.

{
  "id": "8f2b1c40-9a3e-4a1b-9f0c-2d1e5a7b3c4d",
  "status": "queued",
  "ids": [
    "8f2b1c40-9a3e-4a1b-9f0c-2d1e5a7b3c4d"
  ]
}

Every request carries an API key as a bearer token. Keys start with mf_denis_ and are scoped to one workspace.

Authorization: Bearer mf_denis_xxxxxxxxxxxxxxxx

Keys carry a scope: full, send or read. A read key cannot send.

Pass scheduled_at as an ISO 8601 timestamp and the message waits until then. Times are UTC unless you say otherwise.

await densend.emails.send({
  from: "You <[email protected]>",
  to: "[email protected]",
  subject: "A reminder",
  text: "This was scheduled.",
  scheduledAt: new Date("2026-09-01T09:00:00Z"),
});

Each attachment is filename, base64-encoded content, and an optional content_type (defaults to application/octet-stream). 7MB total across all attachments combined, after decoding - not the size of the base64 text itself. Going over returns a 422 naming the actual size, so you find out before the request succeeds, not after.

import { readFileSync } from "node:fs";

await densend.emails.send({
  from: "You <[email protected]>",
  to: "[email protected]",
  subject: "Your invoice",
  text: "Attached.",
  attachments: [
    {
      filename: "invoice.pdf",
      content: readFileSync("./invoice.pdf"), // a Buffer is encoded for you
      contentType: "application/pdf",
    },
  ],
});

Returns the message and its timeline: queued, sent, delivered, bounced, complained.

const email = await densend.emails.get("8f2b1c40-9a3e-4a1b-9f0c-2d1e5a7b3c4d");

console.log(email.status, email.opens, email.clicks);

{
  "id": "8f2b1c40-9a3e-4a1b-9f0c-2d1e5a7b3c4d",
  "to": "[email protected]",
  "from_addr": "[email protected]",
  "subject": "Hello",
  "status": "delivered",
  "direction": "outbound",
  "opens": 0,
  "clicks": 0,
  "created_at": "2026-08-21T09:14:22Z",
  "events": [
    {
      "type": "delivered",
      "detail": null,
      "ts": "2026-08-21T09:14:25Z"
    }
  ]
}

Newest first. Use limit and offset to page, and direction to filter. The total sits in the X-Total-Count header, so you can tell how much is left.

const emails = await densend.emails.list({ limit: 20 });

Anything that speaks SMTP can send through DenSend without touching the API. Useful for WordPress, Django, Rails or any framework with mail already wired up.

Host

smtp.densend.com

Port

587 with STARTTLS

Username

densend

Password

your API key

The password is the API key itself, so it needs the send or full scope. Your exact settings are on the SMTP page in the dashboard.

Failures come back as JSON with a detail field written to be shown to a person, not parsed by a machine.

{
  "detail": "acme.com is not verified yet. Publish its DNS records, then verify it."
}

Limits come from your plan rather than from the API: a monthly allowance, and on some plans a daily one. Going past either returns 402 with a message saying which limit you hit.

Extra emails bought on top of a plan are used only once the monthly allowance is gone, and they do not expire when the period rolls over.