Email API for apps and AI agents.

• Add email to your app

  Send and receive mail from your code with one API key, on as many addresses as you need. Keep each product or client separate.

  Best for: Developers and SaaS teams

  See the email API

• Send from your own domain

  Send as you@yourcompany.com. We show you the DNS records to add, and Runearc checks DNS and Amazon SES readiness for you.

  Best for: Real emails to your customers

  Add your domain

• Let an AI agent use email

  Give your agent its own inbox. It can receive verification codes, read mail and reply.

  Best for: AI agents and automations

  Connect an agent

• Get an email address to try

  Create an inbox and send yourself a test message. No domain or setup needed.

  Best for: Trying Runearc for the first time

  Create an inbox

Using another tool today? Here is what changes, and where the other one is still better.

• From Resend

  Keep the Resend SDK and change one base URL. Receiving, a support inbox and agent inboxes come with the same key.

  Where Resend is better: Stored templates, React Email, open and click tracking, broadcasts, official SDKs in many languages, dedicated IPs and more than one sending region.

  Resend alternative, in detail

• From AgentMail

  Custom domains on the free plan, and sending for your app from the same account as your agents.

  Where AgentMail is better: A larger MCP server with OAuth sign in, Python and Node SDKs, and paid plans you can buy today.

  AgentMail alternative, in detail

• From Mailosaur

  A catch-all where every test makes up its own address, and one API call that waits for its email.

  Where Mailosaur is better: SMS testing, email previews, and plugins for many test frameworks.

  Mailosaur alternative, in detail

• Indie hackersEach product needs auth emails, a support@ address, DNS records and another bill. Then you start the next one.
• SaaS teamsThe sending bill grows with every user, and support@ lives in a separate help desk with its own seats.
• Vibe codersThe app works, but sign up emails never arrive or land in spam, and you are not sure where the email code should even go.
• AI agent buildersAn agent that signs up for things needs a real address, has to catch the verification code, and should never touch your own mailbox.
• QA and test engineersSign up, magic link and password reset flows need a real inbox, and a polling loop that is flaky in parallel.
• Agencies and freelancersEvery client site needs a contact form, a sender domain and a support address, and every teammate needs the right access to each.

• ana@example.comWelcome to Acmequeueddelivered

  li@example.orgReset your passwordqueueddelivered

  sam@example.netYour receiptqueueddelivered

  Send

  Sign up emails, magic links and receipts from your own domain. A Resend compatible API, SMTP, batches of up to 100 and scheduled sends, with delivered, bounced and complained events.

• orders@shop.examplein

  Invoice 0142.pdf

  spfdkimdmarc

  Receive

  Mail to your addresses is stored, threaded and checked for SPF, DKIM and DMARC. Read it with the API or get a webhook.

• DDana Wu My reset link expiredopenclosed

  OOmar Ali Invoice addressopen

  KKim Lee Thanks, it works nowclosed

  Support inbox

  support@ on your domain as a shared inbox: assign, snooze and close conversations, and reply in the customer's thread.

• wait_for_email subject: code

  482913

  codes[0], links[0]

  Agent inboxes

  Give each agent its own address over MCP. wait_for_email blocks until the message arrives and returns its codes and links.

• e2e-0-a1x@k7m3qz.mailbay.emaile2e-1-k9p@k7m3qz.mailbay.emaile2e-2-q4m@k7m3qz.mailbay.emaile2e-3-z7d@k7m3qz.mailbay.emaile2e-0-a1x@k7m3qz.mailbay.emaile2e-1-k9p@k7m3qz.mailbay.emaile2e-2-q4m@k7m3qz.mailbay.emaile2e-3-z7d@k7m3qz.mailbay.email

  Catch-all, one inbox

  Test inboxes

  Any address under your private mailbay.email domain lands in one catch-all, so every test can make up its own address.

• MXmx1.mailbay.dev···

  TXTmb1._domainkey v=DKIM1; k=rsa···

  MXbounce feedback-smtp.us-east-1.amazonses.com···

  TXTbounce v=spf1 include:amazonses.com ~all···

  Guided domain setup

  Add a domain and on Vercel or Cloudflare we write the inbound MX, DKIM, DMARC and Amazon SES return-path records for you. Anywhere else, copy the records and the dashboard checks each one live. Existing MX records are never deleted.

// The Resend SDK, pointed at Runearc. In .env:
//   RESEND_BASE_URL=https://api.mailbay.dev/v1
//   RESEND_API_KEY=mb_live_...
import { Resend } from "resend";

const mailbay = new Resend(process.env.RESEND_API_KEY);

export async function POST(req: Request) {
  const { email } = await req.json();
  const { data, error } = await mailbay.emails.send({
    from: "Acme <team@acme.com>",
    to: email,
    subject: "You're invited to Acme",
    html: "<p>Join your team on Acme.</p>",
  });
  return Response.json(error ?? data, { status: error ? 400 : 200 });
}

Names and logos belong to their owners. They are shown because Runearc works with these tools, not because of a partnership.

Know what happened to every email

Each email you send shows as delivered, delayed, bounced or reported as spam, so you can tell why a password reset never arrived.

Mail we accept is never lost

We only confirm that we received a message after it is safely saved. Mail to an address that does not exist is refused straight away.

One bad address cannot hurt you

If an address bounces or someone reports your email as spam, we stop sending to it for that project.

Deliverability is a shared job. Runearc authenticates your domain, handles bounces and complaints, and pauses harmful traffic. Inbox placement still depends on wanted content, list quality, domain reputation and each mailbox provider's filters.

Global prices shown in USD. See the full pricing page.