Start here
Free
$0- 5,000 emails / month
- 5 inboxes
- Custom domain not included
- 5 GB storage
- No separate daily send cap
- Search, webhooks, MCP, HTML and attachments
Live billing · prices as of 2026-09-27
More inbox and more mail than AgentMail, at a lower price.
Numbers below are the Cooper plans in src/lib/pricing.ts. AgentMail figures are their public list, retrieved 2026-09-27 from AgentMail pricing, AgentMail pay as you go, AgentMail rate limits. AgentMail Startup includes a SOC 2 report. Cooper does not — that is a roadmap, not a certification.
Most agents
Starter
$12/mo- 25,000 emails / month
- 25 inboxes
- 15 custom domains
- 25 GB storage
- No separate daily send cap
- Search, webhooks, MCP, HTML and attachments
POST /api/v1/billing/checkout
{"plan":"starter"}
Fleet
Pro
$99/mo- 250,000 emails / month
- 300 inboxes
- 200 custom domains
- 100 GB storage
- No separate daily send cap
- Search, webhooks, MCP, HTML and attachments
POST /api/v1/billing/checkout
{"plan":"pro"}
Overage
$1 per extra inbox / month, $1 per extra custom domain / month, $1 per 1,000 extra emails / month. AgentMail’s published unit is $2 (pay as you go, 2026-09-27). Hitting an included cap returns 402 with an upgrade link until the subscription includes the next plan or those overage prices.
Side by side with AgentMail
| AgentMail | Cooper | |
|---|---|---|
| Free | $0 · 3 inboxes · 3,000/mo · 100/day · 0 domains | $0 · 5 inboxes · 5,000/mo · no daily cap · 0 domains |
| Entry paid | Developer $20/mo · 10 inboxes · 10,000/mo · 10 domains | Starter $12/mo · 25 inboxes · 25,000/mo · 15 domains |
| Team paid | Startup $200/mo · 150 inboxes · 150,000/mo · 150 domains · SOC 2 report | Pro $99/mo · 300 inboxes · 250,000/mo · 200 domains · SOC 2 not included |
| Overage unit | $2 | $1 |
Startup monthly sends are stated as 150,000 in AgentMail’s pay-as-you-go post and rate-limits doc. The pricing page leaves Emails/month blank and lists 15,000 emails/day. Enterprise on both products is custom — email ops@avatar33.com. Full write-up: /compare/agentmail.
Billing FAQ
- How does an agent start a paid plan?
- POST /api/v1/billing/checkout with {"plan":"starter"} or {"plan":"pro"} and the account’s Bearer key. The response is a Stripe Checkout URL the agent can hand to a person. GET /api/v1/billing returns the plan, usage, and limits. MCP tools: cooper_billing_status and cooper_upgrade_link.
- What happens at the limit?
- Creating an inbox or sending past the plan cap returns HTTP 402 plan_limit_exceeded with upgrade_url. Idempotent retries of a client_id that already sent still return the stored message. Grandfathered accounts (present when billing launched) are not capped.
- Is overage automatic?
- No. Included limits stop at 402. Stripe prices exist for $1 per extra inbox, $1 per extra domain, and $1 per 1,000 emails. A quantity of those prices on the subscription raises the cap. Cooper does not silently bill past the cap.
- Are custom domains on Free?
- No. Free is @cooperemail.com only. Starter and Pro include custom domains. The DNS wizard does not block send, search, or webhooks on the address you already have.