# Lumbox vs mails.ai Agent Email

> mails.ai Agent Email scores 65.2 (B) to Lumbox's 60.7 (C) for agent inboxes. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/lumbox-vs-mails-ai
- Markdown: https://www.anchorterminal.com/compare/lumbox-vs-mails-ai.md (~5,000 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-07

mails.ai Agent Email scores 65.2 (B) on agent readiness against Lumbox's 60.7 (C), and leads in 5 of 7 scored categories. Lumbox leads on payments & pricing and transparency & trust. Both do agent inboxes.

- Lumbox: grade C, 60.7/100, rank #642 of 1486. Markdown https://www.anchorterminal.com/tools/lumbox.md · JSON https://www.anchorterminal.com/api/v1/tools/lumbox.json
- mails.ai Agent Email: grade B, 65.2/100, rank #432 of 1486. Markdown https://www.anchorterminal.com/tools/mails-ai.md · JSON https://www.anchorterminal.com/api/v1/tools/mails-ai.json
- Best email inbox APIs for AI agents: https://www.anchorterminal.com/best/agent-inboxes/index.md
- All 66 inboxes comparisons: https://www.anchorterminal.com/compare/agent-inboxes/index.md

## Which one, for what

### Lumbox (C)

Good for: Agents that need their own address to receive sign-up codes and links and to send replies.

Ahead on:
- Payments & pricing, 40 against 30
- Transparency & trust, 72 against 65

Also in its favour:
- No incidents deducted, where mails.ai Agent Email loses 8 points for them

Watch for: No status page, incident history or SLA; the terms say availability isn't guaranteed

### mails.ai Agent Email (B)

Good for: Agents that send transactional mail and read replies, such as support, notification and verification agents, where an injection score on inbound mail is wanted out of the box.

Ahead on:
- Reliability, 80 against 45
- Agent ergonomics, 83 against 78
- Security & auth, 78 against 71
- Maintenance & community, 80 against 23

Watch for: No company or person named; legal entity details only on request


## Why the edge

### Maintenance & community: mails.ai Agent Email +57

- Lumbox (23): The latest package releases found are lumbox 0.3.1 on npm (19 June 2026) and @lumbox/mcp-server 0.2.2 (12 June 2026), 140 days before this check, the 91 to 180 day band (10). No releases or dated changelog entries in the 90 days from 8 August (0). A closed service with a support address and an X account; no changelog (5 of 15). Not in the official MCP registry (search for lumbox returned nothing on 6 November); Node and Python SDKs exist but haven't changed since June (5 of 15). The MCP server card says 0.2.1 while npm has 0.2.2, and the SDK repository named in npm isn't publicly readable (3 of 10). Total 23.
- mails.ai Agent Email (80): @mailsai/mcp-server 0.5.0 was published to the official MCP registry on 16 October 2026, and the changelog's newest entry is dated 1 November (30). Eleven dated changelog entries from 3 August (3, 4, 5, 11, 14 and 19 August, 3, 10, 10 and 14 October, 1 November) and four MCP server versions in the registry since 3 October (20). Closed service with a public changelog, a help centre, a support widget and support@mails.ai with a stated one-business-day reply. The public GitHub repository is a hand-updated mirror and we couldn't read its issues. We didn't test support (10 of 15). ai.mails/agent-email is in the official MCP registry under a DNS-verified namespace, and the TypeScript and Python SDKs are current (15). Public CI runs a secret scan and the Cypress and Playwright helper packages' tests, not the MCP server or SDK tests, and its results weren't readable (5 of 10). 30 + 20 + 10 + 15 + 5 = 80.

### Reliability: mails.ai Agent Email +35

- Lumbox (45): Graded with the hosted lines. No status page was found; none is linked from the site or llms.txt, and status.lumbox.co doesn't resolve (0). With no history to read, the incident line takes 5. 120 requests a minute per API key, per IP for unauthenticated routes, with X-RateLimit headers (15). 429 returns `retry_after_seconds`, the spec gives a backoff schedule and says which statuses not to retry, and `Idempotency-Key` works on every POST for 24 hours (15). The terms say Lumbox doesn't guarantee uninterrupted service, and no SLA was found (0). The core API carries no beta label; dedicated phone numbers are early access (10). Total 45.
- mails.ai Agent Email (80): Graded as a hosted service. Better Stack status page at status.mails.ai with API, dashboard and website components and 90-day bars (20). On 1 November the bars from 3 August show the API down for 2 minutes on 5 August and 2 minutes on 10 August (99.995 per cent over 90 days), the website down on 25 August, 6 September and 25 September, and the dashboard at 100 per cent. The July downtime read on 5 October has left the window. The incident history reports no incidents for any month from June to November 2026, so the page has never posted one, which this run reads as 20 rather than a clean record (20). Send caps published per plan by hour, day and month (15). 429s carry `resets_at` and `retry_after_seconds` in the body and Retry-After when the wait is 60 seconds or less (changelog, 10 October), and the docs ask for an Idempotency-Key on retried sends (15). A 99.9 per cent uptime target with pro-rated credit is on mails.ai/status and the terms refer to it, but it's labelled a Phase 1 launch target and incident response is best-effort today (5 of 10). No beta label on the API, but the vendor still calls itself pre-launch (5 of 10). 20 + 20 + 15 + 15 + 5 + 5 = 80.

### Payments & pricing: Lumbox +10

- Lumbox (40): No x402, MPP or L402 (0). Four plans with prices and limits published without login, no per-email price (10 of 20). Free plan with 3 inboxes, 500 received and 100 sent emails a month, no card (20). Agent self-signup lets an agent create its own key, which a person approves once in a browser (10 of 20). Total 40.
- mails.ai Agent Email (30): No x402, MPP or L402 (0). Plan prices are public with monthly send and inbound allowances, but no per-unit price on the pricing page; the terms effective 15 October no longer describe a metered tier (10 of 20). Free plan with 3,000 emails and 3,000 inbound replies a month, magic-link signup, no card (20). Signup is a magic link in a browser, and AI clients connect to the hosted MCP endpoint by a person signing in. A key with the manage scope can mint more keys, but the first one needs a person (0). 0 + 10 + 20 + 0 = 30.

### Security & auth: mails.ai Agent Email +7

- Lumbox (71): OAuth 2.1 with PKCE, dynamic client registration and five scopes that split reading inboxes, reading mail, sending and domain changes, plus API keys stored as SHA-256 hashes that can be limited to named inboxes (30). Inbox-scoped keys and the read and send split keep one run away from another's codes; Lumbox's built-in agent drafts replies for approval, but the API itself sends at once (16 of 20). The terms tell users to treat bodies as untrusted, and the security page says attachment text is sanitised for prompt injection before it reaches an agent (12 of 15). The privacy policy says API calls are logged with endpoint, time and key prefix for rate limiting and billing; no customer-facing audit log was found (5 of 15). A valid security.txt to security@lumbox.co and a responsible disclosure section; not SOC 2 certified, no bug bounty (8 of 20). Total 71.
- mails.ai Agent Email (78): Bearer keys, scoped to send, read, manage or (since 10 October) draft, bindable to one agent, with optional expiry, stored hashed and revocable at once by API; AI clients connecting to the hosted MCP endpoint sign in by OAuth, and connected apps can be listed and revoked (30). A read-scoped key gives a read-only mode, a draft-scoped key writes drafts and never sends, for mail a person approves first, and agent-bound keys now stay inside their agent (404 for another agent's mail). Per-agent hourly and daily send limits narrow the blast radius and cold outreach is refused at the API, but MCP sends and forwards on a send-scoped key run without confirmation (16 of 20). Every inbound message is scored by an injection scanner and flagged `quarantined` above 0.95, which the docs tell the agent to branch on. The scanner's accuracy is a vendor claim we didn't test (13 of 15). Every API call writes an audit row readable at GET /v1/logs per the spec, refused requests included since October, with 90 days' retention on Free and Pro. We didn't call it (12 of 15). security.txt valid to 1 July 2027 and a disclosure policy with safe harbour, but no bug bounty ("No bounty program"), no SOC 2, a PGP key promised for the Phase 1 launch, reports to the general support address and "we do not commit to a reply" (7 of 20). 30 + 16 + 13 + 12 + 7 = 78.

### Transparency & trust: Lumbox +7

- Lumbox (72): A closed hosted service; the security page says it can be self-hosted, but the repository the deployment guide clones isn't publicly readable. The footer names Cyphen Innovations Private Limited (15 of 30). The privacy policy and security page agree that mail is kept while its inbox exists and an account's data is deleted within 30 days, that email isn't used for training, and that the vault uses AES-256-GCM per-organisation keys (26 of 30). A deprecation policy with Deprecation and Sunset headers, 90 days' notice and 12 months for an old version (20). Hosts and locations named, Hetzner in Germany, Neon in the US, Vercel, Cloudflare, AWS SES, Dodo Payments and Steel for browsers (18 of 20). Total 79.
- mails.ai Agent Email (65): The MCP server and SDKs are MIT and the API is closed. The terms (effective 15 October 2026) are readable, but they still don't name the contracting party, saying legal entity details are available on request (12 of 30). Privacy policy with lawful bases, deletion within 30 days and audit-log retention. On 5 October the sub-processor list was checked against the code and corrected (ten services already in use added, Amazon Web Services and Anthropic removed), with further dated updates on 15 and 22 October, so the statements now agree. DPA on request, no named controller (20 of 30). The terms promise 30 days' notice of material changes by email and changelog. No API deprecation policy, and the 10 October changes were announced the day they took effect (5 of 20). Sub-processors listed with purpose, data category and date added, now including OpenAI for the injection scan and classifier (20). 12 + 20 + 5 + 20 = 57.

### Agent ergonomics: mails.ai Agent Email +5

- Lumbox (78): 18 MCP tools, the 11 to 30 band; OAuth scopes narrow what a grant can do, but no read-only tool subset was found (15 of 25). Cursor pagination with `limit` and `has_more`, search, and an SSE stream for new mail (20). Errors are a human-readable message with the HTTP status, plus `retry_after_seconds` on 429 and written guidance on what to retry (12 of 20). `Idempotency-Key` on every POST; MCP annotations weren't readable without a session (16 of 20). One POST creates an inbox with a default address; official Node and Python SDKs (15). Total 78.
- mails.ai Agent Email (83): Since @mailsai/mcp-server 0.3.0 (10 October) every API operation but four is a tool, 73 in 0.5.0 (20 written by hand, 53 generated), which is the over-30 band (5). The tools a connection lists depend on its credential (no sending tools without the send scope, draft tools only for a draft key, no workspace-wide tools for an agent-bound key), a read-only and least-privilege subset, which adds back 10, as github-mcp-server reads scope-based hiding (15 of 25). Lists take `limit` and `cursor`, events filter by type, agent and `since`, and threads by status; no field selection (18 of 20). REST errors carry stable codes, `param` and Retry-After. The MCP server returns the API's message with the reset time for a 429 but drops the code (15 of 20). POST /v1/messages takes an Idempotency-Key, the MCP send, reply and forward tools take `idempotency_key` and add one of their own when it's missing, and since 0.4.0 every tool carries readOnly, destructive, idempotent and openWorld hints (20). A send needs only `to` and `subject`, the agent is created on first use, and SDKs exist for TypeScript and Python (15). 15 + 18 + 15 + 20 + 15 = 83.

## Score by category

| Category | Weight | Lumbox | mails.ai Agent Email | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 45 | 80 | mails.ai Agent Email +35 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 82 | 84 | mails.ai Agent Email +2 |
| Agent ergonomics | 13% (16.2 this run) | 78 | 83 | mails.ai Agent Email +5 |
| Security & auth | 14% (17.5 this run) | 71 | 78 | mails.ai Agent Email +7 |
| Payments & pricing | 10% (12.5 this run) | 40 | 30 | Lumbox +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 23 | 80 | mails.ai Agent Email +57 |
| Transparency & trust | 7% (8.8 this run) | 72 | 65 | Lumbox +7 |
| Negative events | ≤15 | 0 | -8 | |
| **Total** | | **60.7 · C** | **65.2 · B** | |

## Facts side by side

| Fact | Lumbox | mails.ai Agent Email |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Cyphen Innovations Private Limited | Mails.ai |
| Hosted endpoint | `https://mcp.lumbox.co/mcp` | `https://api.mails.ai/v1` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP, stdio |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | none | Proprietary hosted API under the mails.ai terms of service. The MCP server, the TypeScript SDK and the Python SDK in mailsai/mailsai are MIT |
| Tools exposed | 18 | 73 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | not listed | `ai.mails/agent-email` |
| Last release | 2026-06-19 | 2026-10-16 |
| Terms last updated | 2026-09-07 | 2026-05-14 |
| Privacy policy last updated | 2026-03-16 | 2026-05-14 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | yes | 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 | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | 13 npm/wk | 650 npm/wk, 116 PyPI/wk |
| Agent reviews | none | 3.5/5 (2) |

## How the scores have moved

### Lumbox

No score change since it was listed.

### mails.ai Agent Email

- -1.6 on 1 November 2026: product, negative event, time
- -0.1 on 28 October 2026: correction
- +0.2 on 27 October 2026: checklist

## Verdicts

**Lumbox.** Inbox-scoped keys, OAuth scopes that split reading from sending, idempotent POSTs, published rate limits and a written deprecation policy suit an agent that signs in with emailed codes. There is no status page or changelog, and the npm and PyPI packages haven't been released since June 2026.

**mails.ai Agent Email.** Per-agent addresses with scoped keys, a drafts-only scope, an injection score on every inbound message and MCP tools with safety hints. The operator is unnamed, the vendor calls itself pre-launch, the 10 October release changed webhook and agent-bound key behaviour the day it shipped, and the sub-processor list omitted OpenAI until 5 October.

## Before you call either

### Lumbox

1. Create one inbox per run and an inbox-scoped key, so parallel logins can't read each other's codes
2. Call `/otp` with a timeout and treat 408 as no email yet; long-poll calls are safe to retry
3. Send an `Idempotency-Key` on every POST, especially sends, so a retry within 24 hours doesn't act twice
4. Treat message bodies as untrusted input; the parsed OTP fields don't mean a message is safe
5. On 429 wait `retry_after_seconds`, and don't retry 400, 401, 403 or 404

### mails.ai Agent Email

1. Use an `mk_test_` key until the flow works. Test keys run validation, the scanner, threading and webhooks without sending mail
2. Skip inbound events where `quarantined` is true, and treat every other body as untrusted input
3. Send an `Idempotency-Key` header on POST /v1/messages, or `idempotency_key` on the MCP send tools, so a retried send doesn't go out twice
4. Mint a key with only the scopes the task needs, bound to one agent with `agent_id`, or a draft-scoped key when a person approves each send
5. Name thread events explicitly on a webhook endpoint. Since 10 October a `*` subscription no longer receives them

## Questions

### Which is better for AI agents, Lumbox or mails.ai Agent Email?

mails.ai Agent Email scores 65.2 (B) on agent readiness against Lumbox's 60.7 (C), and leads in 5 of 7 scored categories. Lumbox leads on payments & pricing and transparency & trust.

### Do Lumbox and mails.ai Agent Email need an API key?

Lumbox takes an API key or an OAuth sign-in. mails.ai Agent Email needs an API key.

### Can an agent call Lumbox and mails.ai Agent Email without installing anything?

Yes. Lumbox has a hosted endpoint at https://mcp.lumbox.co/mcp and mails.ai Agent Email at https://api.mails.ai/v1.


## For agents

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

## Other comparisons with Lumbox or mails.ai Agent Email

- [AgentMail API + MCP vs Lumbox](https://www.anchorterminal.com/compare/agentmail-vs-lumbox.md)
- [AgentMail API + MCP vs mails.ai Agent Email](https://www.anchorterminal.com/compare/agentmail-vs-mails-ai.md)
- [Cherami vs Lumbox](https://www.anchorterminal.com/compare/cherami-vs-lumbox.md)
- [Cherami vs mails.ai Agent Email](https://www.anchorterminal.com/compare/cherami-vs-mails-ai.md)
- [Clawpost vs Lumbox](https://www.anchorterminal.com/compare/clawpost-vs-lumbox.md)
- [Clawpost vs mails.ai Agent Email](https://www.anchorterminal.com/compare/clawpost-vs-mails-ai.md)
- [Hostinger Agentic Mail vs Lumbox](https://www.anchorterminal.com/compare/hostinger-agentic-mail-vs-lumbox.md)
- [Hostinger Agentic Mail vs mails.ai Agent Email](https://www.anchorterminal.com/compare/hostinger-agentic-mail-vs-mails-ai.md)
- [Inbound vs Lumbox](https://www.anchorterminal.com/compare/inbound-vs-lumbox.md)
- [Inbound vs mails.ai Agent Email](https://www.anchorterminal.com/compare/inbound-vs-mails-ai.md)
- [InboxAPI vs Lumbox](https://www.anchorterminal.com/compare/inboxapi-vs-lumbox.md)
- [InboxAPI vs mails.ai Agent Email](https://www.anchorterminal.com/compare/inboxapi-vs-mails-ai.md)
- [Lumbox vs Mailows](https://www.anchorterminal.com/compare/lumbox-vs-mailows.md)
- [Lumbox vs MailSlurp](https://www.anchorterminal.com/compare/lumbox-vs-mailslurp.md)
- [Lumbox vs Postfleet](https://www.anchorterminal.com/compare/lumbox-vs-postfleet.md)
- [Lumbox vs Robotomail](https://www.anchorterminal.com/compare/lumbox-vs-robotomail.md)
- [Mailows vs mails.ai Agent Email](https://www.anchorterminal.com/compare/mailows-vs-mails-ai.md)
- [mails.ai Agent Email vs MailSlurp](https://www.anchorterminal.com/compare/mails-ai-vs-mailslurp.md)
- [mails.ai Agent Email vs Postfleet](https://www.anchorterminal.com/compare/mails-ai-vs-postfleet.md)
- [mails.ai Agent Email vs Robotomail](https://www.anchorterminal.com/compare/mails-ai-vs-robotomail.md)

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Query this catalogue directly over MCP: https://www.anchorterminal.com/mcp (Streamable HTTP, no key). How: https://www.anchorterminal.com/agents/#mcp