Head to head · Agent inboxes · October 2026 research run

Clawpost vs InboxAPI

InboxAPI scores 46.2 (D) on agent readiness against Clawpost's 36.8 (F), and leads in 5 of 7 scored categories. Clawpost leads on schema & documentation and payments & pricing. Both do agent inboxes.

Best email inbox APIs for AI agents · All 66 inboxes comparisons

Which one, for what

Clawpost F

Best for A developer who wants an agent inbox on their own domain and Cloudflare account with a default approval gate.

Ahead on

  • Schema & documentation, 54 against 28
  • Payments & pricing, 60 against 53

Also in its favour

  • Open source

Watch for

One shared API key grants every REST and MCP operation; no scopes or read-only key

InboxAPI D

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

Ahead on

  • Reliability, 33 against 8
  • Agent ergonomics, 61 against 53
  • Security & auth, 57 against 42
  • Maintenance & community, 43 against 2
  • Transparency & trust, 54 against 32

Also in its favour

  • No key needed to call it
  • A hosted endpoint, with nothing to install
  • Runs on your own machine
  • Free to start without a card

Watch for

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

Why the edge

Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.

Maintenance & community InboxAPI +41

Clawpost 2

The last commit was on 1 April 2026, 219 days before this check (0). No releases or commits in the 90 days from 8 August (0). Issue and pull request activity couldn't be read through GitHub's API that day (0, unchecked). Not in the official MCP registry and no published package (0). Dependencies such as agents ^0.0.74 and the MCP SDK ^1.12.1 date from early 2026, and there's no CI (2 of 10). Total 2.

InboxAPI 43

Four versions were tagged on 22 September 2026 and none since (git ls-remote, 4 November). v0.3.20 carries the archive-email alias and other CLI changes since v0.3.19 (25 May), so recency is 43 days (20 of 30, 30 on 9 October). The 90-day line counts dated entries from 6 August, v0.3.20 (full), v0.3.21 (a test fix and release-workflow change, packaging-only, half), and v0.3.22 and v0.3.23, tagged on the same commit as v0.3.21 (half each), 2.5 in all, short of three (0 of 20; the line is 20 or 0). Issues and pull requests per the 9 October reading, not re-read (15 of 25). The 9 October MCP registry search came from its JSON API, which this run doesn't use, and is struck; no entry is credited (0 of 15). CI and CodeQL configured, CI passing on 22 September per the 9 October reading, npm trusted publishing, Cargo.toml on the default branch still at 0.3.14 (8 of 10). 20 + 0 + 15 + 0 + 8 = 43.

Schema & documentation Clawpost +26

Clawpost 54

All 21 MCP tools take typed zod inputs, which the MCP SDK publishes as JSON Schema (25). SKILL.md and AGENTS.md give agent-readable setup in Markdown; no llms.txt (5 of 10). Descriptions are one line each, such as Send an email, with parameter descriptions but no when-not-to-use (8 of 20). Inputs are typed with defaults for limit and offset, but recipients are a comma-separated string and direction isn't an enum in the schema read (9 of 15). The README has request examples and a REST route table; error responses aren't documented (7 of 15). No versioning or changelog (0). Total 54.

InboxAPI 28

Graded on the MCP tools. The 9 October contract reading came from an unauthenticated tools/list call to the hosted endpoint, a request to the product's own endpoint, and is struck. No published document gives the server's input schemas. The tools reference lists 17 tool names with one-line descriptions, which isn't a contract, and the CLI source defines schemas only for its three local tools (0). llms.txt is published (10). The reference's one-liners say what each tool does, and a few say how, such as get_thread taking any Message-ID, with nothing on when not to call them (8 of 20). With the schemas struck, no typed inputs, enums or constraints are published (0). The docs show one sample response, for spotlighting, and no error reference (5 of 15). Releases are tagged with empty notes, there is no changelog, and the hosted tools carry no version (5 of 15). 0 + 10 + 8 + 0 + 5 + 5 = 28.

Reliability InboxAPI +25

Clawpost 8

Graded with the lines for self-hosted software, since each deployer runs their own Worker. No published package; it deploys from the repository with a Deploy to Cloudflare button, Bun and Wrangler, and states the Cloudflare products it needs (8 of 20). No CI workflow or test suite in the repository (0). Open issues couldn't be read, because GitHub's API refused our requests for its rate limit, so the line scores absent (0, unchecked). No tags, releases or changelog; package.json says 0.1.0 (0). Pre-1.0 (0). Total 8.

InboxAPI 33

Graded as a hosted service, because the mail runs on InboxAPI's servers and the CLI is a bridge to them. No status page was found on the site or in the repository (0 of 20), so there is no readable incident history (5 of 30). The limits page, re-read on 4 November, gives 100 requests a minute, 20 a minute on auth calls and five external recipient slots, and says daily and hourly send quotas are enforced without giving numbers (11 of 15, an in-between value kept and flagged). A 429 carries Retry-After per the limits page, which says to wait that many seconds before retrying, and the CLI source adds the wait to the tool error. Sends take no idempotency key (10 of 15). A rate-limit header read from a response on 9 October came from a request to the product's own endpoint and is struck; the award never rested on it. No SLA, and the terms guarantee no availability (0). Nothing on the site marks the service beta, while the CLI is at 0.3.23 and the README says functions may change without notice (7 of 10, in-between, kept and flagged). 0 + 5 + 11 + 10 + 0 + 7 = 33.

Transparency & trust InboxAPI +22

Clawpost 32

The README and SKILL.md say MIT, but no LICENSE file is committed (20 of 30). Self-hosted; the README says mail is stored in the deployer's D1 database with attachments in R2 and sent through Cloudflare Email Service or Resend. No retention or deletion guidance (15 of 30). No deprecation policy (0). No telemetry in the source read; the only outbound calls are to the configured mail provider, Cloudflare's API and the deployer's own webhooks (15 of 20). Total 50.

InboxAPI 54

The CLI is open source under the MIT licence. The hosted mail service is closed, under terms dated 11 September 2026 that name Sitka Capital Pty Ltd as operator and Dini Labs Pty Ltd as owner of the technology (20 of 30). The terms and the privacy policy agree on roles, with the customer as controller of mail content, and the policy lists what is collected. It gives no retention period, and a DPA is available on request only (15 of 30). No deprecation policy. The terms allow functions to be removed at any time, with 14 days' notice only for changes to the terms that reduce a user's rights (3 of 20). No sub-processors are named, and data may be held in Australia and overseas, the United States among them. The CLI asks the npm registry for the latest version once a day and sends the MCP client's name and version to the service in its User-Agent, per the source (5 of 20). Terms and privacy policy still dated 11 September 2026 on 4 November.

Security & auth InboxAPI +15

Clawpost 42

One shared secret for REST and MCP, compared in constant time, with no scopes, expiry or per-client keys (10 of 30). Sender approval, drafts, and an optional allowlist of domains for routing changes limit what an agent can see and change; the key can still send to anyone (14 of 20). Mail from unapproved senders is hidden from all query tools by default, and list_pending returns metadata without bodies, documented as a prompt-injection guard (15). No log of API or tool calls beyond the stored messages (3 of 15). No security policy, advisories or disclosure route for this personal project (0). Total 42.

InboxAPI 57

The CLI holds an access and a refresh token in a local file written with mode 0600 and puts the token into each call, so the model never handles it. Tokens cover the whole account with no scopes, travel in the request body, and can be revoked one at a time or all at once from the CLI (20 of 30). There is no read-only mode. The CLI refuses forward_email without confirm, refuses new recipients unless a flag the model can set itself is passed, and keeps five auth and encryption tools out of MCP. The service caps an account at five external recipients (12 of 20). Inbound mail gets one of four trust levels and untrusted text is datamarked with a per-request marker, tool descriptions warn against following email content, and outbound mail containing a JWT is rejected, per the docs (14 of 15). get_sent_emails shows delivery status and an optional Claude Code hook writes a local activity log. No server-side audit log was found (6 of 15). security.txt returns 404, and no disclosure policy, bounty or certification was found. The repository runs CodeQL and publishes to npm with provenance (5 of 20). Re-read on 4 November, security.txt still answers 404, the repository has no SECURITY.md, and osv.dev lists no advisory for inboxapi or @inboxapi/cli.

Agent ergonomics InboxAPI +8

Clawpost 53

21 tools, the 11 to 30 band (15 of 25). List and search tools take limit, offset and filters by direction, sender, label and archive state (20). Error shapes aren't documented; the code returns JSON errors (8 of 20). No idempotency key for sends and no readOnlyHint or destructiveHint annotations; drafts give a review step (3 of 20). Archived mail is excluded by default and the CLI has a --json mode, but there's no SDK beyond the CLI (7 of 15). Total 53.

InboxAPI 61

The CLI source hides nine auth and encryption tools from MCP clients (five blocked, four internal) and adds local whoami, report_bug and request_feature. The tools reference names 17 tools and the README speaks of 21 tool definitions, so an agent sees between 11 and 30 (15 of 25, plus 2 for the hidden auth tools and the plain-text default, 17). The 28 KB size of the definitions came from the struck tools/list reading and is dropped. The reference describes paginated get_emails, search by sender, subject or date range, and a count tool. Bodies can't be searched (17 of 20, per 9 October, kept). No error codes are documented. The CLI source returns plain messages for refused recipients and rate limits (8 of 20). Sends take no idempotency key. The CLI adds readOnlyHint and destructiveHint to the tools and retries a call once after a token refresh (10 of 20). A send needs three fields and setup needs no configuration. There is no SDK, only the CLI, whose subcommands print JSON (9 of 15). 17 + 17 + 8 + 10 + 9 = 61.

Score by category

CategoryWeight this runClawpostInboxAPIEdge
Reliability16%20833InboxAPI +25
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.25428Clawpost +26
Agent ergonomics13%16.25361InboxAPI +8
Security & auth14%17.54257InboxAPI +15
Payments & pricing10%12.56053Clawpost +7
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.8243InboxAPI +41
Transparency & trust7%8.83254InboxAPI +22
Negative events≤1500
TotalF 36.8/100D 46.2/100

Facts side by side

FactClawpostInboxAPI
KindMCP serverMCP server
VendorFrank HarrisSitka Capital Pty Ltd
Hosted endpointno (local only)https://mcp.inboxapi.ai/mcp
TransportsStreamable HTTP, HTTPstdio, Streamable HTTP
AuthAPI keyNone
PricingFreeFree
x402nono
LicenceMITProprietary hosted service under InboxAPI's terms of service. The CLI on GitHub is MIT
Tools exposed2121
Read-only variant documentednono
llms.txtnoyes
Last release2026-04-012026-09-22
Terms last updatedno document linked2026-09-11
Privacy policy last updatedno document linked2026-09-11
Customer content may train modelsnot read yetnot found in the text
Terms restrict automated accessnot read yetnot found in the text
Terms restrict benchmarkingnot read yetnot found in the text
Terms or service can change without noticenot read yetnot found in the text
Arbitration or class-action waivernot read yetnot found in the text
Popularitynone12 stars, 38 npm/wk

How the scores have moved

Verdicts

Clawpost

A small self-hosted agent inbox whose sender-approval gate keeps unknown senders' mail away from the agent by default, with drafts for human review. It is one developer's project, unchanged since 1 April 2026, with one all-powerful key, no releases, tests or CI.

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

Clawpost

  1. Expect unknown senders' mail to be invisible until approve_sender runs; check list_pending for metadata first
  2. Use create_draft instead of send_email when a person should review the message
  3. Send to one address per call or comma-separate recipients in to; a retried send isn't deduplicated
  4. Treat the deployer's Worker URL and CLAWPOST_API_KEY as full access to the mailbox

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, Clawpost or InboxAPI?

InboxAPI scores 46.2 (D) on agent readiness against Clawpost's 36.8 (F), and leads in 5 of 7 scored categories. Clawpost leads on schema & documentation and payments & pricing.

Do Clawpost and InboxAPI need an API key?

Clawpost needs an API key. InboxAPI needs no key.

Can an agent call Clawpost and InboxAPI without installing anything?

No hosted endpoint is listed for Clawpost. InboxAPI has a hosted endpoint at https://mcp.inboxapi.ai/mcp.

Are Clawpost and InboxAPI open source?

Clawpost is open source (MIT). No open-source release is listed for InboxAPI.

Other comparisons with Clawpost or InboxAPI

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