# Mailchimp Transactional (Mandrill) (slim)

> Transactional email service from Intuit Mailchimp, formerly Mandrill. It sends application email and SMS through an HTTP API, SMTP or a hosted MCP server, with templates, inbound routing, webhooks and reporting, as a paid add-on to a Mailchimp plan.

- Full: https://www.anchorterminal.com/tools/mandrill.md (~8,850 tokens) · this version ~1,930 tokens · JSON https://www.anchorterminal.com/tools/mandrill.json · canonical https://www.anchorterminal.com/tools/mandrill
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · Updated: 2026-10-08

**C · 58.1/100 · rank #459 of 722 · #12 in Email delivery APIs · not agent-ready · confidence medium**


Assessment: A public OpenAPI 3.1 file covers all 99 operations, the docs serve Markdown and llms.txt, and keys can be limited by endpoint and IP address. Sending needs a Standard or Premium Mailchimp plan plus $20 blocks of 25,000 emails. No send idempotency key or SLA was found, and the newest dated release is from 24 March 2026.

## Facts

- Kind: HTTP API · vendor: Intuit Mailchimp · category: Email delivery APIs · legal entity: The Rocket Science Group LLC d/b/a Mailchimp · provenance 77/100
- Endpoint: `https://mandrillapp.com/api/1.4` (HTTP)
- Auth: API key · pricing: Paid · x402: no · licence: Proprietary service under Mailchimp's Standard Terms of Use and Additional Terms. The client libraries are under Mailchimp's own client library licence agreement
- Probe metrics: not measured yet (probes haven't run)
- API: JSON over HTTP, every call a POST to https://mandrillapp.com/api/1.4/ with the key in the body. 99 operations in an OpenAPI 3.1 file. Output as json, xml, yaml or php. The quick start still uses the 1.0 path, which answered on 8 October 2026
- MCP server: Hosted at https://mandrillapp.com/mcp over HTTP, 9 tools, API key as a Bearer token. Without a key it answers JSON-RPC error -32001
- Credentials: API keys created in the web app, several per account, each optionally limited to chosen endpoints and IP addresses. Test keys work only in test mode. No OAuth
- SMTP: smtp.mandrillapp.com on ports 25, 587 or 2525 with STARTTLS, or 465 for SSL. Up to 1,000 recipients a message
- Limits: Hourly sending quota set by reputation and volume, with no published figure. `/messages/search` 20 calls a minute, then 429. Test mode 10,000 messages a day. Demo accounts 25 emails an hour. Scheduling up to one year ahead
- Demo: 500 emails once, to the account's own verified domain only, 25 an hour, 100 inbound a day, no click tracking. Open to free and paid Mailchimp accounts that have not bought blocks before
- Before first send: A Mailchimp account, the Transactional add-on or demo, an API key, and a sending domain verified with DKIM and DMARC records
- Inbound: Add an inbound domain and MX records, then routes post parsed mail to a webhook, in batches of up to 1,000 events about once a minute
- Webhooks: Events batched per URL about once a minute. A failed post is retried up to 20 times at intervals of 15 to 25 minutes
- Data retention: Message content 30 days, bounce details 90 days, raw bounce detail 7 days, backlog 48 hours. The additional terms say retention is not guaranteed
- Client libraries: Node `@mailchimp/mailchimp_transactional` and Python `mailchimp-transactional`, both 1.4.1 from 24 March 2026, plus PHP and Ruby, generated from one specification
- Subaccounts: Separate reputation, reporting and optional fixed hourly quota per sender under one account, managed by API
- Certifications: SOC 2 reports and ISO 27001 per mailchimp.com/about/security. A responsible disclosure programme with no rewards
- Status: status.mailchimp.com, with Mailchimp Transactional as one component since August 2025 and event history by month
- Prices: Email block, 1 to 20 blocks $0.80 per 1,000 emails; Email block, 21 to 40 blocks $0.72 per 1,000 emails; Email block, 41 to 80 blocks $0.64 per 1,000 emails; Email block, 81 to 120 blocks $0.56 per 1,000 emails; Email block, 121 to 160 blocks $0.48 per 1,000 emails; Email block, 161 blocks or more $0.40 per 1,000 emails; Dedicated IP $29.95 per month (plan)

- Scores: Reliability 53, Performance pending, Schema & documentation 79, Agent ergonomics 60, Security & auth 68, Payments & pricing 35, Task success pending, Maintenance & community 28, Transparency & trust 71 · total over the 7 assessed categories
- Why: Reliability, Graded on the hosted Transactional API with the hosted lines. · Schema & documentation, An OpenAPI 3.1 file with all 99 operations is public at mailchimp.com/developer/openapi/api-reference-2.json, and a Swagger 2.0 copy sits in… · Agent ergonomics, Graded on the API. · Security & auth, API keys are created and revoked in the web app, several to an account, and each can be limited to chosen endpoints and to IP addresses. · Payments & pricing, No x402, MPP or L402 (0). · Maintenance & community, The newest dated release we found is version 1.4.1 of the specification and the Node and Python libraries on 24 March 2026, 198 days before… · Transparency & trust, Closed service with published terms and a named contracting entity.
- Sources: 26, open questions: 8, both in the full twin
- Capabilities: email.send, email.templates, email.inbound, email.domains, email.analytics
- JSON: https://www.anchorterminal.com/api/v1/tools/mandrill.json
- Verify (for the vendor): the badge `https://www.anchorterminal.com/badges/mandrill.svg` or a link to https://www.anchorterminal.com/tools/mandrill from a page on mailchimp.com or one of its subdomains, or the README of github.com/mailchimp/mailchimp-client-lib-codegen, then `POST https://www.anchorterminal.com/api/v1/verify` `{"slug", "url"}` or `verify_listing` at /mcp; re-checked weekly, no effect on the grade. Snippets in the full twin.

## Before you call it

1. Send every call as POST with the key in the JSON body as `key`. The MCP server takes the same key as `Authorization: Bearer`
2. Use a test API key while building. Test sends are free, capped at 10,000 a day, and deliver nothing
3. Verify the sending domain with DKIM and DMARC first. Mail from an unverified domain is rejected with the reason `unsigned`
4. Keep `/messages/search` under 20 calls a minute and set `limit` (default 100, maximum 1,000). There is no offset, so use an activity export for more
5. For a restricted key that must also use the MCP server, enable the AI Agents permission group on the key

## Connect

```bash
npm install @mailchimp/mailchimp_transactional
```

```bash
curl -sS -X POST "https://mandrillapp.com/api/1.0/users/ping" \
  --header 'Content-Type: application/json' \
  --data-raw '{ "key": "YOUR_API_KEY" }'
```

```bash
claude mcp add --transport http mctx-mcp https://mandrillapp.com/mcp \
  -H "Authorization: Bearer YOUR_API_KEY"
```
Full config and headless snippets are in the full page. Through letme (picks today, calling later): https://letme.dev/mandrill

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| --- | --- | --- | --- | --- |
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