High Flying Email Platform

Email for developers and their teams.

Agents and humans, one platform. A transactional API for your stack, a shared inbox for your team, and their own inboxes for your agents. Send, receive, and auto-reply across unlimited domains, free.

Get started — free Read the docs →

Transactional API ·Team inbox ·Agent inboxes ·Deliverability built in

Inbox · hello@myapp.ai 6 tagged

support

Re: refund for order #1042

A Ada Lovelace <ada@acme.io>

Loading…

Reply as support@myapp.ai

Reply sent

receive → reply round trip

POST /your/webhook HTTP/1.1Content-Type: application/json{ "from": "ada@example.com", "to": "hello@myapp.ai", "subject": "Re: invoice #1042", "text": "Looks good — approved!", "messageId": "<a1b2c3@mail.example.com>", "receivedAt": "2026-06-19T17:42:10Z"} ← 200 OK — your endpoint

// your app or agent repliesPOST /v1/send HTTP/1.1Host: api.mailkite.devAuthorization: Bearer mk_live_3a9f…{ "from": "hello@myapp.ai", "to": "ada@example.com", "subject": "Re: invoice #1042", "in_reply_to": "<a1b2c3@mail.example.com>", "html": "<p>Thanks — receipt attached.</p>"} ← 202 Accepted{ "id": "msg_2Hk9…", "status": "queued" }

Received 17:42:10 · replied 17:42:11 — no human in the loop.

agent · mcp.mailkite.dev

prompt Check support@ and reply to Ada confirming the refund cleared.

mailkite.list({ tag: "support" }) → 1 message

mailkite.get("msg_2Hk9") → "…confirm the refund went through?"

mailkite.send({ to: "ada@acme.io", reply_to: "msg_2Hk9" }) → 202 queued

agent Replied to Ada — refund for #1042 confirmed as cleared. ✓

Same tools your agent gets over MCP, an AI skill, or REST.

Our Tier-1 Networks

Amazon SES Cloudflare Postmark

For developers

A transactional email API for your stack

Send and receive from your app in a few lines — Next.js, Nuxt, Node, Python, PHP, Go, Ruby, and more. One shape everywhere, plus CLI, REST, SMTP, and IMAP.

send.ts

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>",
});

Install GitHub Docs

app/api/send/route.ts

import { MailKite } from "mailkite";

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

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

Install GitHub Docs

app/routes/send.tsx

import { MailKite } from "mailkite";

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

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

Install GitHub Docs

server/api/send.post.ts

import { MailKite } from "mailkite";

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

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

Install GitHub Docs

server.ts

import express from "express";
import { MailKite } from "mailkite";

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

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

Install GitHub Docs

src/index.ts

import { Hono } from "hono";
import { MailKite } from "mailkite";

const app = new Hono();

app.post("/send", async (c) => {
  const mk = new MailKite(c.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>",
  });
  return c.json({ id, status });
});

export default app;

Install GitHub Docs

src/pages/api/send.ts

import type { APIRoute } from "astro";
import { MailKite } from "mailkite";

const mk = new MailKite(import.meta.env.MAILKITE_API_KEY);

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

Install GitHub Docs

server.ts

import { MailKite } from "mailkite";

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

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

Install GitHub Docs

src/worker.ts

// wrangler.jsonc → "compatibility_flags": ["nodejs_compat"]
import { MailKite } from "mailkite";

export default {
  async fetch(_req: Request, env: Env) {
    const mk = new MailKite(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>",
    });
    return Response.json({ id, status });
  },
};

Install GitHub Docs

app/api/send/route.ts

import { MailKite } from "mailkite";

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

// Deploys as a Vercel Function — same code on Netlify or any Node runtime.
export async function POST() {
  const { id, status } = await mk.send({
    from: "hello@myapp.ai",
    to: "ada@example.com",
    subject: "Your invoice #1042",
    html: "<p>Thanks! Receipt attached.</p>",
  });
  return Response.json({ id, status });
}

Install GitHub Docs

handler.ts

import { MailKite } from "mailkite";

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

export const handler = async () => {
  const { id, status } = await mk.send({
    from: "hello@myapp.ai",
    to: "ada@example.com",
    subject: "Your invoice #1042",
    html: "<p>Thanks! Receipt attached.</p>",
  });
  return { statusCode: 200, body: JSON.stringify({ id, status }) };
};

Install GitHub Docs

supabase/functions/send/index.ts

import { MailKite } from "npm:mailkite";

const mk = new MailKite(Deno.env.get("MAILKITE_API_KEY"));

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

Install GitHub Docs

main.ts

import { MailKite } from "npm:mailkite";

const mk = new MailKite(Deno.env.get("MAILKITE_API_KEY"));

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

Install GitHub Docs

send.py

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>",
})

Install GitHub Docs

views.py

import os
from django.http import JsonResponse
from mailkite import MailKite

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

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

Install GitHub Docs

app.py

import os
from flask import Flask, jsonify
from mailkite import MailKite

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

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

Install GitHub Docs

main.py

import os
from fastapi import FastAPI
from mailkite import MailKite

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

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

Install GitHub Docs

send.php

<?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>',
]);

Install GitHub Docs

routes/web.php

<?php
use MailKite\Client;

Route::post('/send', function () {
    $mk = new Client(env('MAILKITE_API_KEY'));
    $res = $mk->send([
        'from' => 'hello@myapp.ai',
        'to' => 'ada@example.com',
        'subject' => 'Your invoice #1042',
        'html' => '<p>Thanks! Receipt attached.</p>',
    ]);
    return response()->json($res);
});

Install GitHub Docs

src/Controller/SendController.php

<?php
use MailKite\Client;
use Symfony\Component\HttpFoundation\JsonResponse;
use Symfony\Component\Routing\Attribute\Route;

class SendController
{
    #[Route('/send', methods: ['POST'])]
    public function send(): JsonResponse
    {
        $mk = new Client($_ENV['MAILKITE_API_KEY']);
        return new JsonResponse($mk->send([
            'from' => 'hello@myapp.ai',
            'to' => 'ada@example.com',
            'subject' => 'Your invoice #1042',
            'html' => '<p>Thanks! Receipt attached.</p>',
        ]));
    }
}

Install GitHub Docs

send.rb

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>"
)

Install GitHub Docs

app/controllers/sends_controller.rb

class SendsController < ApplicationController
  def create
    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>"
    )
    render json: res
  end
end

Install GitHub Docs

app.rb

require "sinatra"
require "mailkite"

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

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

Install GitHub Docs

main.go

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>",
})

Install GitHub Docs

Send.java

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>"
));

Install GitHub Docs

SendController.java

@RestController
public class SendController {
    private final MailKite mk = new MailKite(System.getenv("MAILKITE_API_KEY"));

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

Install GitHub Docs

terminal

npm i -g @mailkite/cli && mailkite login

mailkite send --from hello@myapp.ai --to ada@example.com \
  --subject "Your invoice #1042" --html "<p>Thanks! Receipt attached.</p>"

mailkite messages tail   # watch inbound arrive

GitHub Docs

terminal

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>"
  }'

GitHub Docs

terminal

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

GitHub Docs

send.ts

// No SDK — one POST with the built-in fetch.
const res = await fetch("https://api.mailkite.dev/v1/send", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.MAILKITE_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    from: "hello@myapp.ai",
    to: "ada@example.com",
    subject: "Your invoice #1042",
    html: "<p>Thanks! Receipt attached.</p>",
  }),
});

const { id, status } = await res.json();

GitHub Docs

send.py

# No SDK — one POST with requests.
import os, requests

res = requests.post(
    "https://api.mailkite.dev/v1/send",
    headers={"Authorization": f"Bearer {os.environ['MAILKITE_API_KEY']}"},
    json={
        "from": "hello@myapp.ai",
        "to": "ada@example.com",
        "subject": "Your invoice #1042",
        "html": "<p>Thanks! Receipt attached.</p>",
    },
)

print(res.json())  # { "id": "msg_…", "status": "queued" }

GitHub Docs

.env

# Point WordPress, a CRM, or any app that speaks SMTP at the relay.
SMTP_HOST=smtp.mailkite.dev
SMTP_PORT=587            # STARTTLS · 465 for implicit TLS
SMTP_USER=mailkite       # any username works
SMTP_PASS=mk_live_…      # your MailKite API key — not a separate SMTP password
SMTP_FROM=you@your-verified-domain.dev

GitHub Docs

send.ts

import nodemailer from "nodemailer";

const tx = nodemailer.createTransport({
  host: "smtp.mailkite.dev",
  port: 587,                 // STARTTLS · use 465 for implicit TLS
  auth: {
    user: "mailkite",        // any username works
    pass: process.env.MAILKITE_API_KEY, // your mk_live_… key
  },
});

await tx.sendMail({
  from: "hello@myapp.ai",    // an address on a verified domain
  to: "ada@example.com",
  subject: "Your invoice #1042",
  html: "<p>Thanks! Receipt attached.</p>",
});

GitHub Docs

settings.py

import os

EMAIL_HOST = "smtp.mailkite.dev"
EMAIL_PORT = 587                     # STARTTLS · 465 for implicit TLS
EMAIL_USE_TLS = True
EMAIL_HOST_USER = "mailkite"         # any username works
EMAIL_HOST_PASSWORD = os.environ["MAILKITE_API_KEY"]  # your mk_live_… key
DEFAULT_FROM_EMAIL = "hello@myapp.ai"  # an address on a verified domain

# Anywhere in your app:
# from django.core.mail import send_mail
# send_mail("Your invoice #1042", "Thanks! Receipt attached.",
#           "hello@myapp.ai", ["ada@example.com"])

GitHub Docs

.env

MAIL_MAILER=smtp
MAIL_HOST=smtp.mailkite.dev
MAIL_PORT=587                    # STARTTLS · 465 for implicit TLS
MAIL_USERNAME=mailkite           # any username works
MAIL_PASSWORD=mk_live_…          # your MailKite API key
MAIL_ENCRYPTION=tls
MAIL_FROM_ADDRESS=hello@myapp.ai # an address on a verified domain

# Then Mail::to('ada@example.com')->send(new InvoiceMail) just works.

GitHub Docs

config/environments/production.rb

config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
  address:              "smtp.mailkite.dev",
  port:                 587,                     # STARTTLS · 465 for implicit TLS
  user_name:            "mailkite",              # any username works
  password:             ENV["MAILKITE_API_KEY"], # your mk_live_… key
  enable_starttls_auto: true,
}
# Action Mailer now sends from any address on a verified domain.

GitHub Docs

read_inbox.py

# Read your MailKite inbox from any IMAP client or library — over IMAPS,
# with a scoped app-password (Settings → IMAP), never your API key.
import imaplib

M = imaplib.IMAP4_SSL("imap.mailkite.dev", 993)
M.login("agent@yourdomain.com", "mk_imap_…")  # your IMAP app-password
M.select("INBOX")
typ, data = M.search(None, "UNSEEN")

GitHub Docs

Send transactional mail, replies, and broadcasts with one POST
Receive every inbound message as clean JSON at your webhook
Official SDKs for six languages — one API shape across all languages to send/receive email
Scoped, idempotent API keys; DKIM-signed sending on your domain

For your team

A shared inbox your team actually reads

Marketers, support, and developers work the same inbox @yourdomain — every address in one place, tagged and triaged, reply as any of them. No per-seat tax on support@ or billing@.

Every address on every domain, in one inbox
Tag, assign, and reply as any address on the domain
Marketers, support, and devs — one place, no context-switching
Pay per human who logs in, never per address

Inbox · hello@myapp.ai 6 tagged

support

Re: refund for order #1042

A Ada Lovelace <ada@acme.io>

Loading…

Reply as support@myapp.ai

Reply sent

For your agents

Agent inboxes, with instant auto-reply

Give any agent a real catch-all inbox — it receives, reads, and replies over MCP, an AI skill, or plain REST. Turn on auto-reply and it triages, answers, filters spam, tags, and escalates on its own.

A dedicated inbox per agent, per task, or per tenant
MCP-native — send, list, read, and reply as tools
Auto-reply: triage, answer, tag, and escalate without a server
Sign-ups, verification, and 2FA codes handled autonomously

Deliverability

Emails fly to the inbox, not spam.

Every message goes out authenticated — SPF, DKIM, and DMARC configured for you — and routed across tier-1 networks to the highest-deliverability tier your sending earns. You ship features; we keep you out of the spam folder.

SPF DKIM DMARC

delivery path

Auto-routed across Cloudflare · Amazon SES + more — AI-tuned per domain, promoted to the highest tier your sending earns.

The fundamentals, handled

SPF Sender Policy Framework

Authorizes MailKite's servers to send for your domain. Receivers check the sending host against your published record — we keep it aligned.

DKIM DomainKeys Identified Mail

Every message is cryptographically signed with a key on your domain, so receivers can prove it wasn't altered in transit. We publish and rotate the keys.

DMARC Domain-based Message Authentication

Ties SPF and DKIM to the From: address recipients actually see, and tells inboxes to trust aligned mail. Configured and monitored for you.

Warm pools from day one

New domains start on shared IP pools we've already warmed, with an established reputation — so your very first send lands. No weeks-long warm-up, no reputation to babysit.

Best-path routing

Your mail rides Cloudflare, Amazon SES, Postmark, and other tier-1 networks. MailKite routes every message down the path most likely to land it — and reroutes if one degrades, so delivery never rides on a single provider.

Climbs on its own

MailKite learns how each domain sends and promotes it to the highest-deliverability tier its sending earns — AI-tuned as you go. Inbox placement gets better with nothing to configure.

Also handled Warmed sending domain Reverse DNS (PTR) TLS in transit Bounce & complaint handling Feedback loops List-Unsubscribe headers

Get your API key How domain auth works →

See how deliverability works →

Switched from SendGrid, inbox placement went from ~92% to ~99% in two weeks.

Mark — AdRender.app

How it works

Live in three steps

One domain setup covers every email job — for code, for people, and for agents.

Point your domain

Add the MX, SPF, and DKIM records we generate. We verify them and your whole domain goes live — send and receive, both directions.

Wire up each address

Send a webhook, open the shared inbox, or hand an address to an agent — pick per address. Grab an API key for your code.

Run it all in one place

Transactional mail, your team's inbox, and your agents' inboxes — one platform, one bill, one domain setup.

Featured on

AI Agents

StartupBase

The AiSurf

One email platform for your whole team

Developers, humans, and agents — send, receive, and auto-reply on one domain. Unlimited domains, free to start.

Get started free Read the docs

Compliant by design

GDPR Compliant

PCI Compliant

CCPA Compliant