Cooper Email is an email API that gives each AI agent its own inbox. Free is $0 and includes 5 inboxes and 5,000 emails a month.
Retrieved 2026-11-05 · Updated 2026-10-11
On the lists re-read 2026-11-05, Cooper’s free tier is larger and its entry plan costs less. AgentMail is ahead where you need a SOC 2 report, WebSockets, or SMTP. Both let an agent sign itself up.
Sources: AgentMail pricing · AgentMail pay as you go · AgentMail rate limits · AgentMail llms.txt (agent sign-up) · Cooper pricing
Free is for a builder testing a few agents. Starter is for one production agent on your domain. Pro is for an inbox per customer or an agent fleet. AgentMail alternative is the short answer with a copy-paste install.
On the lists re-read 2026-11-05, Starter is $12/month and AgentMail Developer is $20/month. Pro is $99/month and Startup is $200/month. Extra inboxes, domains, or 1,000 sends are $1 on Cooper and $2 on AgentMail. Enterprise on both sides is custom and is not quoted here.
Cooper Free is 5 inboxes, 5,000 emails/month, and 1 custom domain, with no separate daily cap and no product footer. AgentMail Free is 3 inboxes, 3,000 emails/month, 100/day, 3 GB, 1 custom domain, and a “Sent via AgentMail” footer. AgentMail's pricing page lists 1 custom domain on Free; the rate-limits doc still says Free domains None, and this number matches the pricing page.
Cooper has no SOC 2 report (see https://cooperemail.com/security), no WebSocket endpoint, and no SMTP or IMAP. AgentMail’s Startup plan includes a SOC 2 report, and its pricing page lists WebSockets and an SMTP relay. Enterprise there offers EU region, BYO cloud, and dedicated IPs. AgentMail also has a larger ecosystem and more SDK installs.
Yes. AgentMail’s sign-up is POST /v0/agent/sign-up with a human_email and username, then the human verifies an OTP. Cooper’s is POST /api/v1/onboard, or the cooper_onboard MCP tool, with a username. owner_email is optional. Both have a hosted MCP server. Cooper’s is https://cooperemail.com/mcp.
Choose AgentMail if you need a SOC 2 report, WebSockets, SMTP, or the larger ecosystem. Choose Cooper if you want the larger published free tier, the lower entry price, no footer on free mail, or drafts that wait for a verified human owner. The table is the list of figures. If a number here disagrees with the vendor page, use the vendor page.
Agents ask
Same answers as the FAQ page.
On the lists re-read 2026-11-05, Cooper Free is 5 inboxes and 5,000 emails/month with no daily cap. AgentMail Free is 3 inboxes, 3,000 emails/month, and 100/day. Starter is $12/month and AgentMail Developer is $20/month. Pro is $99/month and AgentMail Startup is $200/month. Extra inboxes, domains, or 1,000 sends are $1 on Cooper and $2 on AgentMail. AgentMail Startup includes a SOC 2 report. Cooper does not.
Cooper Free is 5 inboxes, 5,000 emails/month, and 1 custom domain, with no separate daily cap and no product footer. AgentMail Free, retrieved 2026-11-05, is 3 inboxes, 3,000 emails/month, 100/day, 1 custom domain, and a “Sent via AgentMail” footer. AgentMail's pricing page lists 1 custom domain on Free; the rate-limits doc still says Free domains None, and this number matches the pricing page.
Stay when you need a SOC 2 report (AgentMail lists one on Startup and Enterprise; Cooper has none), WebSockets, or an SMTP relay. AgentMail Enterprise also lists EU region, BYO cloud, and dedicated IPs. AgentMail has a larger ecosystem and more SDK installs. Those points are from their public pages retrieved 2026-11-05. Compare: https://cooperemail.com/compare/agentmail.
Create a Cooper inbox with POST /api/v1/onboard, save the API key, and point the agent’s MCP config or HTTP client at https://cooperemail.com. There is no mailbox import. Historical mail stays where it is. A custom domain moves by publishing the DNS records from POST /api/v1/domains, which starts on Starter. Compare the published limits at https://cooperemail.com/compare/agentmail before you switch.
Cooper is HTTP email for autonomous agents: one POST /api/v1/onboard returns a Bearer key and username@cooperemail.com, inbound arrives as a signed webhook, and every message on the account is full-text searchable. AgentMail is a mature agent-mail API with inboxes and threads; its published Free tier is 3,000 emails/month, 100/day, 3 inboxes, and 1 custom domain (agentmail.to/pricing, 2026-11-05). AgentMail's pricing page lists 1 custom domain on Free; the rate-limits doc still says Free domains None, and this number matches the pricing page. Resend is an excellent transactional sender — inbound is webhook-only, with no persistent searchable inbox. The Gmail API cannot create inboxes programmatically and typically OAuths a human mailbox, which is the wrong isolation model for agents. Cooper’s bet is one-request onboard, account-wide FTS, 1 custom domain on Free, and OpenAPI + MCP + webhooks in one surface.