Sending email

Send API

One endpoint, one key. The same address that receives can send — transactional mail, replies, and broadcasts go out over your own authenticated domain, DKIM-signed and aligned so they land in the inbox.

Send a message

POST /v1/send with an API key. The from address must be on a verified domain. Pick your language — the choice is remembered across the docs.

send a message

Dashboard → Send
From     hello@myapp.ai
To       ada@example.com
Subject  Your invoice #1042
Body     Thanks! Receipt attached.
Click  [ Send ]

Email ada@example.com from hello@myapp.ai
with subject "Your invoice #1042" and body "Thanks! Receipt attached."

import { MailKite } from "mailkite";

const mk = new MailKite(process.env.MAILKITE_API_KEY);

const { id, status } = await mk.send({
  from: "hello@myapp.ai",
  to: "ada@example.com",
  subject: "Your invoice #1042",
  html: "<p>Thanks! Receipt attached.</p>",
});

import os
from mailkite import MailKite

mk = MailKite(os.environ["MAILKITE_API_KEY"])

res = mk.send({
    "from": "hello@myapp.ai",
    "to": "ada@example.com",
    "subject": "Your invoice #1042",
    "html": "<p>Thanks! Receipt attached.</p>",
})

<?php
$mk = new \MailKite\Client(getenv('MAILKITE_API_KEY'));

$res = $mk->send([
    'from' => 'hello@myapp.ai',
    'to' => 'ada@example.com',
    'subject' => 'Your invoice #1042',
    'html' => '<p>Thanks! Receipt attached.</p>',
]);

MailKite mk = new MailKite(System.getenv("MAILKITE_API_KEY"));

Object res = mk.send(Map.of(
    "from", "hello@myapp.ai",
    "to", "ada@example.com",
    "subject", "Your invoice #1042",
    "html", "<p>Thanks! Receipt attached.</p>"
));

mk := mailkite.New(os.Getenv("MAILKITE_API_KEY"))

res, err := mk.Send(mailkite.Message{
	From:    "hello@myapp.ai",
	To:      "ada@example.com",
	Subject: "Your invoice #1042",
	HTML:    "<p>Thanks! Receipt attached.</p>",
})

require "mailkite"

mk = Mailkite::Client.new(ENV["MAILKITE_API_KEY"])

res = mk.send(
  "from" => "hello@myapp.ai",
  "to" => "ada@example.com",
  "subject" => "Your invoice #1042",
  "html" => "<p>Thanks! Receipt attached.</p>"
)

curl https://api.mailkite.dev/v1/send \
  -H "Authorization: Bearer $MAILKITE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "hello@myapp.ai",
    "to": "ada@example.com",
    "subject": "Your invoice #1042",
    "html": "<p>Thanks! Receipt attached.</p>"
  }'

response

← 202 Accepted
{ "id": "msg_2Hk9…", "status": "queued" }

A 202 Accepted means the message was queued for delivery. Use the returned id to look it up later via the Messages API.

Request fields

Field	Type	Notes
`from`	string	Required. An address on a verified domain.
`to`	string · array	Required. One address or a list.
`subject`	string	Subject line — required unless a template supplies it.
`html`	string	HTML body. Provide `html`, `text`, or both.
`text`	string	Plain-text body. Recommended alongside `html`.
`templateId`	string	Send a saved template — a user template (`tpl_…`) or base template (`base_…`); explicit subject/html/text override it.
`templateData`	object	Values for the template's `{{merge_tags}}` (e.g. `{ "name": "Ann" }`). HTML values are auto-escaped.
`cc` / `bcc`	string · array	Optional additional recipients.
`replyTo`	string	Optional `Reply-To` address.
`attachments`	array	Each: `{ filename, url }` (fetched by us) or `{ filename, content }` (base64).
`inReplyTo`	string	A `threadId`/Message-ID to reply in-thread.

 
Every snippet above is the official client library —
    same shape in Node, Python, PHP, Java, Go, and Ruby — or raw curl.
 Replying in-thread
 
To reply to something you received, set inReplyTo to the inbound
    event's threadId. The reply threads correctly in the
    recipient's client:
      reply.json   
 {
  "from": "support@myapp.ai",
  "to": "ada@example.com",
  "subject": "Re: invoice #1042",
  "text": "Approved — thanks!",
  "inReplyTo": "<a1b2c3@mail.example.com>"
}
 
 Attachments
 Attach files two ways:
  By URL — { filename, url }. We fetch it at send time. Best for files you already host.
 Inline — { filename, content, contentType } with base64 content. Best for small, generated files.
 
 Deliverability
 
Outbound is DKIM-signed and SPF/DMARC-aligned automatically on your verified
    domain — there's nothing to configure beyond
publishing your DNS records. Always send a
text part alongside html, keep your
from consistent, and warm new domains gradually for the best
    inbox placement.
 
See every parameter and response in the
API reference.