MailKite

What MailKite is

MailKite is an email API for developers, teams and AI agents that handles both directions of email. Its homepage headline is "Email for every product you ship", and the pitch is that you receive any message as a webhook and send with one API, across unlimited domains and mailboxes, for free. It covers transactional email, replies and broadcasts on the sending side, and parsed inbound email on the receiving side, with a shared team inbox and agent inboxes built on the same service. The company behind it is SendHub LLC, doing business as MailKite, with an address in Sheridan, Wyoming, and the blog is written by its founder, Gabe. MailKite is in beta and offers 50% off the first year as a founding rate for the first 1,000 customers.

Sending

Sending takes a few lines in most stacks. The homepage shows the same call in official SDKs for six languages, Node.js, Python, PHP, Ruby, Go and Java, with one API shape across all of them, and in framework examples for Next.js, Remix, Nuxt, Express, Hono, Astro, Bun, Django, Flask, FastAPI, Laravel, Symfony, Rails, Sinatra and Spring Boot. Serverless runtimes are covered too: Cloudflare Workers, Vercel Functions, AWS Lambda, Supabase Edge and Deno Deploy. A call takes a sender, recipient, subject and HTML body and returns a message ID and status. There is also a CLI, plain REST with cURL or wget, and code that uses no SDK at all.

For software that already speaks SMTP, such as WordPress, a CRM, Nodemailer, Django, Laravel or Rails, you point it at smtp.mailkite.dev on port 587 with STARTTLS or 465 for implicit TLS. Any username works and the password is your MailKite API key, so there is no separate SMTP password to manage. Mail must come from an address on a verified domain, and sending is DKIM-signed on your domain. API keys are scoped and idempotent. The homepage lists Amazon SES, Cloudflare and Postmark as MailKite's Tier-1 networks.

A template playground helps with the first emails. It holds 10 transactional templates, including a welcome email, email verification with a code and a payment receipt, each with variables such as name, code, amount and date. You can pick a light, dark or minimal theme, match your product's colors, edit the content and send a test to yourself, and no account is needed to edit.

Receiving email as a webhook

Inbound email is where MailKite puts the most detail. A blog post by the founder walks through the setup. You add a domain in the dashboard or with the CLI, and MailKite returns the DNS records to publish: an MX record pointing at its edge, plus SPF, DKIM and DMARC records. Once the MX record propagates, which the post says usually takes under 5 minutes, the domain starts receiving. You then register a webhook URL.

From then on every email to any address on that domain is parsed and POSTed to your endpoint as JSON, signed with your account's webhook secret so you can verify the HMAC signature before trusting it. The payload carries an ID and thread ID, sender and recipients, subject, plain text and HTML bodies, a timestamp, attachments with filename, content type, size and a download URL, and an auth object with the SPF, DKIM, DMARC and spam verdicts. MailKite checks those on every inbound message, and you can either enforce them in your handler or rely on its edge to filter spoofed mail. Attachments of any type are extracted and stored, with no size limit beyond the sender's SMTP constraints. Routes can send specific addresses to different endpoints, and the post describes delivery from the MX edge to your webhook as sub-second.

The post names the cases it is built for: teams with several products on several domains, AI agents that need structured email in real time, transactional workflows where an email is the trigger, such as support tickets and notification routing, and processing attachments like PDFs, images and CSV files.

Team inbox, IMAP and agents

The shared inbox brings every address on every domain into one place for marketers, support and developers. Messages can be tagged and assigned, anyone can reply as any address on the domain, and pricing is per person who logs in, never per address, so support@ and billing@ carry no seat cost. Inboxes can also be read over IMAPS from any client or library with a scoped app password rather than the API key.

For AI agents, MailKite runs a hosted MCP server at mcp.mailkite.dev with browser sign-in over OAuth, plus a local version for static keys and offline use. The homepage gives setup snippets for Claude Code, Cursor, Claude Desktop, VS Code, Windsurf, Gemini, Codex and chat agents, and an agent skill teaches coding agents the whole lifecycle of domains, DNS, webhooks, sending and inbound mail. Agents use the MCP tools to send, read inbound mail and reply.

Free tier and pricing

The founder's post answers the free tier question directly: unlimited domains are free, sending and receiving are free within generous limits, and no credit card is required to start. The closing call to action adds that overage is graceful, never a hard cut, and that you can get a live API key in under five minutes. Exact limits and paid rates sit on a separate pricing page. MailKite Server, the open-source email server, is offered for teams that want to self-host.

Support and community

Help comes through the documentation, step-by-step guides, a Discussions forum where users ask questions, request features and show what they built, a blog with deep dives on email and agents, and a hand-picked directory of email and agent tools. A contact page and an AI assistant on the site answer questions about MailKite.

Who it suits

MailKite suits developers who want sending and receiving in one API: SaaS teams sending receipts and verification emails, products that turn incoming email into tickets or tasks, companies running several products on separate domains, and builders of AI agents that need their own inboxes. The free domains and no-card start make it easy to try on a side project, and the shared inbox gives support and marketing a place to work from the same addresses.

It is a young service in beta, and its sending runs over the partner networks it names. Marketers who want a campaign builder with lists and automation are not its main audience, even though broadcasts can be sent through the API.