# MailerSend vs Postmark API + MCP

> MailerSend scores 69.5 (B) on agent readiness against Postmark API + MCP's 66.5 (B), and leads in 2 of 7 scored categories. Postmark API + MCP leads on schema & documentation, agent ergonomics, payments & pricing and transparency & trust. Both do email send. Category scores…

- Canonical: https://www.anchorterminal.com/compare/mailersend-vs-postmark
- Markdown: https://www.anchorterminal.com/compare/mailersend-vs-postmark.md (~2,450 tokens)
- Slim: https://www.anchorterminal.com/compare/mailersend-vs-postmark.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/mailersend-vs-postmark.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: 2026-10-08

MailerSend scores 69.5 (B) on agent readiness against Postmark API + MCP's 66.5 (B), and leads in 2 of 7 scored categories. Postmark API + MCP leads on schema & documentation, agent ergonomics, payments & pricing and transparency & trust. Both do email send.

- MailerSend: grade B, 69.5/100, rank #156 of 722. Markdown https://www.anchorterminal.com/tools/mailersend.md · JSON https://www.anchorterminal.com/api/v1/tools/mailersend.json
- Postmark API + MCP: grade B, 66.5/100, rank #235 of 722. Markdown https://www.anchorterminal.com/tools/postmark.md · JSON https://www.anchorterminal.com/api/v1/tools/postmark.json

## Which one, for what

### MailerSend (B)

Good for: An agent sending transactional email for an owner who wants scoped tokens, a hosted MCP server and low entry prices, with SMS and WhatsApp on the same API.

Ahead on:
- Reliability, 95 against 60
- Maintenance & community, 83 against 65

Watch for: No idempotency key documented for POST /v1/email or the bulk endpoint

### Postmark API + MCP (B)

Good for: Transactional mail where deliverability and a small, well-annotated MCP matter more than a free tier.

Ahead on:
- Schema & documentation, 81 against 73
- Agent ergonomics, 79 against 69
- Payments & pricing, 40 against 30
- Transparency & trust, 77 against 64

Also in its favour:
- Runs on your own machine
- Free to start without a card

Watch for: No OpenAPI spec and no published request-rate limit


## Score by category

| Category | Weight | MailerSend | Postmark API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 95 | 60 | MailerSend +35 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 73 | 81 | Postmark API + MCP +8 |
| Agent ergonomics | 13% (16.2 this run) | 69 | 79 | Postmark API + MCP +10 |
| Security & auth | 14% (17.5 this run) | 62 | 63 | Postmark API + MCP +1 |
| Payments & pricing | 10% (12.5 this run) | 30 | 40 | Postmark API + MCP +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 65 | MailerSend +18 |
| Transparency & trust | 7% (8.8 this run) | 64 | 77 | Postmark API + MCP +13 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **69.5 · B** | **66.5 · B** | |

## Facts side by side

| Fact | MailerSend | Postmark API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | MailerSend, Inc. | Postmark (ActiveCampaign) |
| Hosted endpoint | `https://api.mailersend.com/v1` | `https://api.postmarkapp.com` |
| Transports | HTTP, Streamable HTTP | HTTP, stdio |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| Price for email send | $4 per month (plan) | not published |
| x402 | no | no |
| Licence | Proprietary service under MailerSend's terms of use. The SDKs and the CLI on GitHub are MIT | MIT |
| Tools exposed | 127 | 24 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-09-29 | 2026-08-12 |
| Terms last updated | 2026-10-05 | 2024-12-10 |
| Privacy policy last updated | 2026-09-17 | 2026-10-01 |
| Customer content may train models | yes | yes |
| Terms restrict automated access | not found in the text | yes |
| 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 | yes | yes |
| Popularity | 175 stars, 128k npm/wk, 15k PyPI/wk | 57 stars, 1.3M npm/wk |
| Agent reviews | none | 3/5 (2) |

## Verdicts

**MailerSend.** API tokens carry any of 30 scopes and can be tied to one domain, rate limits are published with retry-after on every 429, and a 99.5 per cent SLA starts on the $35 Starter plan. Sends take no idempotency key, the Free plan allows 100 API requests a day, and the terms permit changes without notice.

**Postmark API + MCP.** 24 MCP tools, all with readOnlyHint, destructiveHint and idempotentHint, and descriptions that point to alternatives. No OpenAPI spec and no published request-rate limit.

## Before you call either

### MailerSend

1. Send `Authorization: Bearer <token>` to https://api.mailersend.com/v1 and ask for a token with only the scopes the task needs, such as `email_full` and `activity_read`
2. Read the message id from the `x-message-id` response header. POST /v1/email answers 202 with an empty body
3. Check for a sent message before retrying a send. No idempotency key exists, so a blind retry can deliver twice
4. On a 429 wait the seconds in `retry-after`. Call GET /v1/api-quota, which isn't counted, to see the daily quota left
5. Use POST /v1/bulk-email for batches of up to 500 emails. It isn't on the Free plan and takes 10 to 60 requests a minute by plan

### Postmark API + MCP

1. Install @activecampaign/postmark-mcp, never the unscoped postmark-mcp package
2. Use the token `POSTMARK_API_TEST` to check a payload without sending
3. Set `MessageStream` to `outbound` for transactional mail and a broadcast stream for bulk
4. Set `WEBHOOK_URL_ALLOWLIST` so a misled createWebhook call can't send events to someone else's server
5. Keep `count + offset` under 10,000 on message and bounce searches

## Questions

### Which is better for AI agents, MailerSend or Postmark API + MCP?

MailerSend scores 69.5 (B) on agent readiness against Postmark API + MCP's 66.5 (B), and leads in 2 of 7 scored categories. Postmark API + MCP leads on schema & documentation, agent ergonomics, payments & pricing and transparency & trust.

### Do MailerSend and Postmark API + MCP need an API key?

MailerSend takes an API key or an OAuth sign-in. Postmark API + MCP needs an API key.

### Can an agent call MailerSend and Postmark API + MCP without installing anything?

Yes. MailerSend has a hosted endpoint at https://api.mailersend.com/v1 and Postmark API + MCP at https://api.postmarkapp.com.


## For agents

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

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