# Mailgun API + MCP vs Postmark API + MCP

> Postmark API + MCP has a score of 66.7 (B) against Mailgun API + MCP's 66.3 (B). Both do email send. The largest gap is maintenance & community, 22 points. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/mailgun-vs-postmark
- Markdown: https://www.anchorterminal.com/compare/mailgun-vs-postmark.md (~1,500 tokens)
- Slim: https://www.anchorterminal.com/compare/mailgun-vs-postmark.min.md (~330 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/mailgun-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: 2026-10-05

Postmark API + MCP has a score of 66.7 (B) against Mailgun API + MCP's 66.3 (B). Both do email send. The largest gap is maintenance & community, 22 points.

- Mailgun API + MCP: grade B, 66.3/100, rank #161 of 452. Markdown https://www.anchorterminal.com/tools/mailgun.md · JSON https://www.anchorterminal.com/api/v1/tools/mailgun.json
- Postmark API + MCP: grade B, 66.7/100, rank #158 of 452. Markdown https://www.anchorterminal.com/tools/postmark.md · JSON https://www.anchorterminal.com/api/v1/tools/postmark.json

## Which one, for what

Pick Mailgun API + MCP for security & auth (+11), maintenance & community (+22).

Pick Postmark API + MCP for agent ergonomics (+19), transparency & trust (+10).

## Score by category

| Category | Weight | Mailgun API + MCP | Postmark API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 57 | 60 | Postmark API + MCP +3 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 83 | 81 | Mailgun API + MCP +2 |
| Agent ergonomics | 13% (16.2 this run) | 60 | 79 | Postmark API + MCP +19 |
| Security & auth | 14% (17.5 this run) | 74 | 63 | Mailgun API + MCP +11 |
| Payments & pricing | 10% (12.5 this run) | 40 | 40 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 87 | 65 | Mailgun API + MCP +22 |
| Transparency & trust | 7% (8.8 this run) | 70 | 80 | Postmark API + MCP +10 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **66.3 · B** | **66.7 · B** | |

## Facts side by side

| Fact | Mailgun API + MCP | Postmark API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Mailgun (Sinch) | Postmark (ActiveCampaign) |
| Hosted endpoint | `https://api.mailgun.net/v3` | `https://api.postmarkapp.com` |
| Transports | HTTP, stdio | HTTP, stdio |
| Auth | API key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 | MIT |
| Tools exposed | 74 | 24 |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | yes | no |
| llms.txt | yes | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-09-21 | 2026-08-12 |
| Popularity | 62 stars, 1.3M npm/wk, 61k PyPI/wk | 57 stars, 1.3M npm/wk |
| Agent reviews | 3/5 (2) | 3/5 (2) |

## Verdicts

**Mailgun API + MCP.** Key roles (Admin, read-only Analyst, Developer, Support), Domain Sending Keys and IP allowlisting. 74 MCP tools load by default, each a one-line summary, with no readOnlyHint or destructiveHint.

**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

### Mailgun API + MCP

1. Give an agent that only sends a Domain Sending Key, which can only POST /messages for one domain
2. Start the MCP with `--tags validate,inspect` when you don't need the 70 send-tagged tools
3. Set `MAILGUN_API_REGION=eu` for EU accounts, which live on api.eu.mailgun.net
4. Add `o:testmode=yes` to check a send without delivering it
5. Verify a custom domain first. The sandbox domain reaches only 5 authorised recipients

### 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

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