Choose AgentMail when you run many agents that each need an address they can read and reply from, such as one inbox per customer. It replaces stitching a sending API to your own mail storage. Teams that only need two or three agent inboxes beside app email will find Resend simpler.
What changed
AgentMail, founded in 2025 and part of Y Combinator's Summer 2025 batch, is an email inbox API for AI agents. Developers create inboxes programmatically, and each one stores threads that agents read and answer through webhooks, websockets, SDKs or a hosted MCP server. Its differentiator is treating the inbox, not the sent message, as the unit.
About AgentMail
AgentMail was founded in 2025 in San Francisco by Haakam Aujla (CEO), Michael Kim (CTO) and Adi Singh, and went through Y Combinator's Summer 2025 batch. Its Launch HN post described the product as email for your AI rather than AI for your email, and drew 169 points and 169 comments.
The difference from a transactional sender is that the inbox is the product. You create inboxes through the API as easily as you create a database row, every inbox keeps its messages as threads with labels and drafts, and new mail reaches your agent by webhook, by websocket, or by a polling webhook that needs no public endpoint. Pods keep each customer's inboxes and domains apart, which is what a company building email into its own agent product needs. There is a hosted MCP server, an official OpenClaw plugin, a guide for the Claude Agent SDK, and a sign-up API that lets an agent request its own account, which stays restricted to mailing its human until that person verifies it.
It suits teams running many agents that each need an address: support desks with one inbox per customer, quote-sourcing agents, and personal agents such as Hermes Agent or OpenClaw. A product that mostly sends receipts and only needs two or three agent inboxes may be better off adding Inboxes to Resend. For send-only notifications, Postmark costs less per message, Amazon SES costs less again, and builders already on Workers can route inbound mail for free with Cloudflare Email Service.
AgentMail completed its first SOC 2 Type II audit in 2025 and runs separate US and EU environments, with the EU region sold on Enterprise. Agent Armor, an opt-in Labs feature, scans received mail for prompt injection and marks suspicious messages for review, and allowlists and blocklists limit who an agent can write to. For the bigger picture of agents that act on your behalf, see our guide to personal AI agents.
AgentMail sits in Hokai's directory of email services with SendGrid, the high-volume incumbent it is not trying to replace. Giving an agent an inbox is the email version of giving it a phone number, which our explainer on what AgentPhone is for covers, and the OpenClaw playbook walks through wiring channels like this into a personal agent. Read our approval-gate guide before letting any agent reply to strangers.
Plans and pricing
No card is needed for Free ($0). Developer $20/mo with 10 inboxes, 10,000 emails/month and 10 custom domains; Startup $200/mo with 150 inboxes, 15,000 emails/day and 150 domains; Enterprise custom with unlimited inboxes, EU cloud, BYO cloud and dedicated IPs. Add-ons on Developer and Startup: $2/mo per extra inbox, $2/mo per extra domain, $2/mo per extra 1,000 sends, $5/mo per extra seat ($19.20 or $48 a year on yearly plans).
Early-stage startups can apply for a free month on Startup. Prices checked on agentmail.to on 6 November 2026.
Server plans
| Plan | Storage | Price |
|---|---|---|
| Free Cloud · 3 inboxes, 1 custom domain, 3,000 emails a month, footer on sent mail · United States | 3 GB | $0/mo |
| Developer Cloud · 10 inboxes, 1,000 sends a day, 2 seats, email support · United States | 10 GB | $20/mo |
| Startup Cloud · 150 inboxes, unlimited storage, 10 seats, SOC 2 report · United States | — | $200/mo |
| Enterprise Cloud · Unlimited inboxes, white-label, BYO cloud, OIDC/SAML SSO, SLA · United States · European Union | — | — |
Key Features
- Inboxes created by API: One API call creates an inbox with its own address, and every inbox stores mail as threads with labels, drafts, attachments and scheduled sends.
- Three ways to hear about new mail: Agents get new messages through signed webhooks, websockets, or polling webhooks built on Svix that need no public endpoint or tunnel.
- Pods for multi-tenancy: Pods isolate inboxes, domains and data per customer, with scoped API keys and webhook filtering for products that resell email to their users.
- Agent Armor: An opt-in Labs feature that gives each received message a clear or review verdict for prompt injection, in Monitor or Hold mode.
- Hosted MCP server: mcp.agentmail.to speaks Streamable HTTP with an x-api-key header and is listed on every plan, including Free.
- Agent self sign-up: An agent can request its own key; until its human verifies, it gets a single inbox and may only send to that human.
Strengths
- The only provider here where inboxes are priced and rate-limited as the main unit, which fits fleets of agents better than a per-domain sender.
- Real-time delivery by websocket means an agent can wait for a reply or a login code without running a public web server.
- Built-in prompt-injection screening and send allowlists address the two risks of an agent inbox that most email APIs leave to you.
Weaknesses
- Young company with a team of 10 on Y Combinator's page, so long-term pricing and roadmap carry more risk than an incumbent's.
- Its docs and pricing page disagreed on free-plan limits on 6 November 2026 (the docs said no monthly cap), so check the live page before planning.
- Free mail carries a Sent via AgentMail footer, EU hosting and dedicated IPs need Enterprise, and 24-hour message expiry is early-access only.
Frequently Asked Questions
What are AgentMail's pricing plans in 2026?
Developer costs $20 a month for 10 inboxes and 10,000 emails, Startup costs $200 a month for 150 inboxes and up to 15,000 emails a day, and Enterprise is quoted, per the pricing page read on 6 November 2026. Extra capacity on the paid plans is sold in $2 blocks: one more inbox, one more domain, or 1,000 more monthly sends, with seats at $5. Yearly billing brings each $2 add-on to $19.20 a year.
What do you get on AgentMail's free tier?
The Free plan needs no credit card and gives you 3 inboxes, 1 custom domain, 3,000 emails a month with a 100-a-day ceiling, 3 GB of storage and 2 team members. Mail sent from it carries a Sent via AgentMail footer, and support is the Discord community. An agent that signs itself up starts tighter still, until its human verifies the account.
What are the best alternatives to AgentMail?
Resend now offers stored, threaded Inboxes beside its sending API, which suits a product that needs only a handful of agent addresses. Cloudflare Email Service gives Workers users free inbound routing and an onEmail hook in its Agents SDK, but you keep the messages yourself. Amazon SES is the low-cost route if you will build storage, threading and safety on top.
AgentMail or Resend: which should you pick?
Pick AgentMail when inboxes are the thing you are scaling: Startup includes 150 of them, and websockets, pods and Agent Armor are built for many agents. Pick Resend when you already send app email there and want three or four agent inboxes on the same domain without a second vendor. Note that Resend counts received mail against its sending quota; AgentMail's docs describe its caps as sending limits.
What does it take to start using AgentMail?
Create a free account in the console, take an API key, and install the SDK with npm install agentmail or pip install agentmail, then create an inbox and send. To give a coding or personal agent access without code, add the hosted MCP server with your key in the x-api-key header. Add a custom domain and its DNS records before you send to anyone outside your team.
Top Alternatives
- Resend: Pick AgentMail for dozens of agent inboxes and websocket delivery; pick Resend when a few inboxes sit beside existing app email.
- Cloudflare Email Service: Pick AgentMail for stored threads with no plumbing; pick Cloudflare if you already run Workers and will store mail yourself.
- Amazon SES: Pick AgentMail to skip building storage and threading; pick Amazon SES when raw per-message cost outweighs engineering time.
- Postmark: Pick AgentMail when the agent must hold conversations; pick Postmark for one-way transactional mail.
Hokai guides that mention AgentMail
- Best Email APIs for AI Agents in 2026: Inbox or Webhook?: Six email APIs for AI agents compared: which give an agent a real inbox, what 10,000 emails each way cost, free-plan catches, retention and safety controls.