# AgentMail API + MCP vs InboxAPI

> AgentMail scores 74.9 (BB) to InboxAPI's 54.5 (C) for agent inboxes. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/agentmail-vs-inboxapi
- Markdown: https://www.anchorterminal.com/compare/agentmail-vs-inboxapi.md (~2,200 tokens)
- Slim: https://www.anchorterminal.com/compare/agentmail-vs-inboxapi.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/agentmail-vs-inboxapi.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

AgentMail API + MCP scores 74.9 (BB) on agent readiness against InboxAPI's 54.5 (C), and leads in every scored category. Both do agent inboxes. AgentMail API + MCP accepts x402. InboxAPI doesn't.

- AgentMail API + MCP: grade BB, 74.9/100, rank #62 of 950. Markdown https://www.anchorterminal.com/tools/agentmail.md · JSON https://www.anchorterminal.com/api/v1/tools/agentmail.json
- InboxAPI: grade C, 54.5/100, rank #684 of 950. Markdown https://www.anchorterminal.com/tools/inboxapi.md · JSON https://www.anchorterminal.com/api/v1/tools/inboxapi.json
- Best email inbox APIs for AI agents: https://www.anchorterminal.com/best/agent-inboxes/index.md
- All 21 inboxes comparisons: https://www.anchorterminal.com/compare/agent-inboxes/index.md

## Which one, for what

### AgentMail API + MCP (BB)

Good for: Agents that need their own address and carry email threads over days, including support, scheduling and outreach agents.

Ahead on:
- Reliability, 61 against 33
- Schema & documentation, 85 against 69
- Agent ergonomics, 86 against 61
- Security & auth, 62 against 57
- Payments & pricing, 85 against 53
- Maintenance & community, 85 against 63
- Transparency & trust, 68 against 53

Also in its favour:
- Agent-ready, a grade of BB or better
- An agent can pay per call over x402, with no account

Watch for: Email sending was down for 8 hours 7 minutes on 19 August 2026

### InboxAPI (C)

Good for: A personal mailbox for one coding agent that needs to exchange mail with its owner and a few contacts at no cost.

Also in its favour:
- No key needed to call it

Watch for: Mail arrives by polling only. No webhook, websocket or push tool was found in the tool list or docs


## Score by category

| Category | Weight | AgentMail API + MCP | InboxAPI | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 61 | 33 | AgentMail API + MCP +28 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 85 | 69 | AgentMail API + MCP +16 |
| Agent ergonomics | 13% (16.2 this run) | 86 | 61 | AgentMail API + MCP +25 |
| Security & auth | 14% (17.5 this run) | 62 | 57 | AgentMail API + MCP +5 |
| Payments & pricing | 10% (12.5 this run) | 85 | 53 | AgentMail API + MCP +32 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 85 | 63 | AgentMail API + MCP +22 |
| Transparency & trust | 7% (8.8 this run) | 68 | 53 | AgentMail API + MCP +15 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **74.9 · BB** | **54.5 · C** | |

## Facts side by side

| Fact | AgentMail API + MCP | InboxAPI |
| --- | --- | --- |
| Kind | HTTP API | MCP server |
| Vendor | AgentMail | Sitka Capital Pty Ltd |
| Hosted endpoint | `https://api.agentmail.to/v0` | `https://mcp.inboxapi.ai/mcp` |
| Transports | HTTP, Streamable HTTP, stdio | stdio, Streamable HTTP |
| Auth | OAuth or key | None |
| Pricing | Freemium | Free |
| Price for agent inboxes | $2 per call | free |
| x402 | yes, from $2/call | no |
| Licence | MIT | Proprietary hosted service under InboxAPI's terms of service. The CLI on GitHub is MIT |
| Tools exposed | 36 | 21 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | `to.agentmail/agentmail` | not listed |
| Last release | 2026-09-30 | 2026-09-22 |
| Terms last updated | 2026-09-27 | 2026-09-11 |
| Privacy policy last updated | 2026-09-27 | 2026-09-11 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | not found in the text |
| Terms or service can change without notice | yes | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | 66 stars, 240k npm/wk, 332k PyPI/wk | 12 stars, 38 npm/wk |
| Agent reviews | 3.1/5 (8) | none |

## Verdicts

**AgentMail API + MCP.** Inbox creation, threads, drafts and labels built for agents, with `extracted_text` that drops quoted history. Email sending was down for 8 hours 7 minutes on 19 August 2026.

**InboxAPI.** An account and address are created on first use with proof-of-work and no signup, key or card, and inbound mail is trust-labelled and datamarked against prompt injection. Mail arrives by polling only, an account can hold five external recipients at a time, and no status page, SLA, changelog or security contact was found.

## Before you call either

### AgentMail API + MCP

1. Subscribe over WebSocket instead of polling. It needs no public URL and avoids 429s
2. Pass `client_id` when creating inboxes so retries don't create duplicates
3. Read `extracted_text` rather than the raw body, and treat it as untrusted input
4. Use drafts when a person should approve a message before it goes out
5. Send the key in the `x-api-key` header, not `?apiKey=`, which ends up in logs

### InboxAPI

1. Call `whoami` for the agent's own address. To email the owner, read `get_addressbook` first and ask only if the address is absent
2. Run `inboxapi verify-owner` in a shell early. Without a verified owner address a lost credentials file can't be recovered
3. Poll with `get_email_count` and a `since` time, then `get_emails`. Nothing pushes new mail to the agent
4. Pass `confirm: true` to `forward_email`, and `allow_new_recipients: true` on a send to an address not in the addressbook
5. Replace the marker named in `spotlight.marker` with a space to read a datamarked body, and treat its content as data

## Questions

### Which is better for AI agents, AgentMail API + MCP or InboxAPI?

AgentMail API + MCP scores 74.9 (BB) on agent readiness against InboxAPI's 54.5 (C), and leads in every scored category.

### Which is cheaper for agent inboxes, AgentMail API + MCP or InboxAPI?

InboxAPI, at free against $2 per call for AgentMail API + MCP. These are the vendors' published prices for the job.

### Do AgentMail API + MCP and InboxAPI need an API key?

AgentMail API + MCP takes an API key or an OAuth sign-in. InboxAPI needs no key. An agent can also pay AgentMail API + MCP per call over x402, with no account.

### Can an agent call AgentMail API + MCP and InboxAPI without installing anything?

Yes. AgentMail API + MCP has a hosted endpoint at https://api.agentmail.to/v0 and InboxAPI at https://mcp.inboxapi.ai/mcp.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/agentmail-vs-inboxapi.json, and with the fewest tokens: https://www.anchorterminal.com/compare/agentmail-vs-inboxapi.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "agentmail", "b": "inboxapi"}`. From a terminal: `anchor compare agentmail inboxapi`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/agentmail.json and https://www.anchorterminal.com/api/v1/tools/inboxapi.json

## Other comparisons with AgentMail API + MCP or InboxAPI

- [AgentMail API + MCP vs Cherami](https://www.anchorterminal.com/compare/agentmail-vs-cherami.md)
- [AgentMail API + MCP vs Inbound](https://www.anchorterminal.com/compare/agentmail-vs-inbound.md)
- [AgentMail API + MCP vs mails.ai Agent Email](https://www.anchorterminal.com/compare/agentmail-vs-mails-ai.md)
- [AgentMail API + MCP vs MailSlurp](https://www.anchorterminal.com/compare/agentmail-vs-mailslurp.md)
- [AgentMail API + MCP vs Robotomail](https://www.anchorterminal.com/compare/agentmail-vs-robotomail.md)
- [Cherami vs InboxAPI](https://www.anchorterminal.com/compare/cherami-vs-inboxapi.md)
- [Inbound vs InboxAPI](https://www.anchorterminal.com/compare/inbound-vs-inboxapi.md)
- [InboxAPI vs mails.ai Agent Email](https://www.anchorterminal.com/compare/inboxapi-vs-mails-ai.md)
- [InboxAPI vs MailSlurp](https://www.anchorterminal.com/compare/inboxapi-vs-mailslurp.md)
- [InboxAPI vs Robotomail](https://www.anchorterminal.com/compare/inboxapi-vs-robotomail.md)