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AgentiSend and AgentMail
Pick AgentMail if the job is giving each agent its own inbox and identity, because inboxes, agent self-signup and code capture are their product and we do not sell any of the three; pick us if the risk you are managing is outbound, where a per-key budget, an approval queue, a kill switch and a published enforcement ladder decide what a looping agent can do to your domain. The figures below are from AgentMail’s published pricing, API reference and legal pages, captured 14 August 2026, and from this product’s published OpenAPI, pricing document and enforcement policy.
| What matters | AgentiSend | AgentMail |
|---|---|---|
| An inbox object per agent | No inbox object. Inbound mail arrives on a domain you have verified and is read with GET /emails/receiving, including the raw message and its attachments. | Inboxes are the product: create one per agent, with threads, drafts and a persistent searchable history. 3 inboxes free, 10 on Developer, 150 on Startup. |
| An agent signing itself up and reading its own code | Not offered. An account is created by a person. | agent.sign_up plus agent.verify gives an agent its own account against a human address, and an unverified agent may only mail that address. |
| A spending limit per key | Every key is created with a send budget and refuses at agent_budget_exceeded. POST /limits/kill-all stops every key at once and writes an audit row. | Plan-level monthly and daily caps (10,000 a month and 1,000 a day on Developer) apply to the account. No per-key budget and no account-wide stop are in the published API. |
| Holding a send for a person to approve | A send that matches an approval rule is queued instead of sent and returns approval_required. A person approves or rejects it, and the queue is its own endpoint. | No approval queue in the published API. Allow and block lists decide what an inbox accepts, not what an agent may send. |
| Price at 10,000 emails a month | $9 a month on Starter, which covers 30,000 emails, so $0.30 per 1,000 at the inclusion. | $20 a month on Developer for 10,000 emails, which is $2.00 per 1,000. That price buys inboxes, not volume. |
| What a refusal tells you | code, message, fix, docs_url and retryable on every 4xx, for all published operations. | A rejected send returns 403 message_rejected and names the endpoint that fixes it. The same idea, on the inbound path. |
| A retry never sends twice | Idempotency-Key on every mutating endpoint, remembered for 7 days. | No idempotency key is documented on the send path. |
| What the model can call | 34 MCP tools, each declaring whether it only reads and whether it destroys, with resources, prompts, and tools written for an agent rather than for an endpoint: preflight_email, why_was_this_not_sent, get_agent_budget, get_kill_switch_state, request_approval. | 24 MCP tools over the same inbox, message, thread and draft surface. |
| What happens before an account is stopped | Published lines: warn at 2% bounce or 0.05% complaints, pause at 4% or 0.08%, over a rolling 7 days, never below 100 delivered-or-bounced sends. POST /trust/appeal puts it in front of a person within 24 hours. | No published enforcement thresholds and no appeal endpoint. The terms reserve suspension at the provider’s discretion. |
| Audited security reports | None yet. No SOC 2 report and no penetration-test letter exist, and /security says so. | SOC 2 is listed from the Startup plan at $200 a month. |
| How long the log keeps a message | 30 days on Starter, 90 on Pro and during the 14-day trial, 180 on Scale, published per tier as retention_days. | Stored history is part of the inbox and sold as a count of inboxes. No retention period is published. |
Sources
- An inbox object per agent. Ours: GET /emails/receiving in the published OpenAPI. AgentMail pricing and API reference, agentmail.to (captured 14 Aug 2026).
- An agent signing itself up and reading its own code. Ours: the account endpoints in the published OpenAPI have no agent signup. AgentMail agent quickstart, agentmail.to (captured 14 Aug 2026).
- A spending limit per key. Ours: POST /limits/keys and POST /limits/kill-all. AgentMail pricing and API reference, agentmail.to (captured 14 Aug 2026).
- Holding a send for a person to approve. Ours: the agent-actions endpoints in the published OpenAPI and /docs/guides/approvals. AgentMail API reference, agentmail.to (captured 14 Aug 2026).
- Price at 10,000 emails a month. Ours: /pricing.json Starter tier. AgentMail pricing page, agentmail.to (captured 14 Aug 2026).
- What a refusal tells you. Ours: /docs/errors. AgentMail error reference, agentmail.to (captured 14 Aug 2026).
- A retry never sends twice. Ours: the published OpenAPI. AgentMail API reference, agentmail.to (captured 14 Aug 2026).
- What the model can call. Ours: /docs/guides/mcp and the tool list the server advertises. AgentMail MCP documentation, agentmail.to (captured 14 Aug 2026).
- What happens before an account is stopped. Ours: /policy/enforcement, GET /trust/thresholds and POST /trust/appeal. AgentMail terms of service, agentmail.to/legal (captured 14 Aug 2026).
- Audited security reports. Ours: /security. AgentMail pricing page, agentmail.to (captured 14 Aug 2026).
- How long the log keeps a message. Ours: /pricing.json retention_days per tier. AgentMail pricing and docs, agentmail.to (captured 14 Aug 2026).