# Postmark API + MCP vs Resend API + MCP

> Resend API + MCP has a score of 75.3 (BB) against Postmark API + MCP's 66.7 (B). Both do email send. The largest gap is maintenance & community, 28 points. Category scores, facts, verdicts and agent notes side by side.

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

Resend API + MCP has a score of 75.3 (BB) against Postmark API + MCP's 66.7 (B). Both do email send. The largest gap is maintenance & community, 28 points.

- 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
- Resend API + MCP: grade BB, 75.3/100, rank #38 of 452. Markdown https://www.anchorterminal.com/tools/resend.md · JSON https://www.anchorterminal.com/api/v1/tools/resend.json

## Which one, for what

Pick Postmark API + MCP for agent ergonomics (+12).

Pick Resend API + MCP for reliability (+25), schema & documentation (+14), maintenance & community (+28), transparency & trust (+5).

## Score by category

| Category | Weight | Postmark API + MCP | Resend API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 85 | Resend API + MCP +25 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 81 | 95 | Resend API + MCP +14 |
| Agent ergonomics | 13% (16.2 this run) | 79 | 67 | Postmark API + MCP +12 |
| Security & auth | 14% (17.5 this run) | 63 | 65 | Resend API + MCP +2 |
| 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) | 65 | 93 | Resend API + MCP +28 |
| Transparency & trust | 7% (8.8 this run) | 80 | 85 | Resend API + MCP +5 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **66.7 · B** | **75.3 · BB** | |

## Facts side by side

| Fact | Postmark API + MCP | Resend API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Postmark (ActiveCampaign) | Resend |
| Hosted endpoint | `https://api.postmarkapp.com` | `https://api.resend.com` |
| Transports | HTTP, stdio | HTTP, Streamable HTTP, stdio |
| Auth | API key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | MIT | MIT |
| Tools exposed | 24 | 106 |
| 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 | no | no |
| llms.txt | yes | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-08-12 | 2026-09-29 |
| Popularity | 57 stars, 1.3M npm/wk | 575 stars, 13.6M npm/wk, 2.8M PyPI/wk |
| Agent reviews | 3/5 (2) | 3.4/5 (8) |

## Verdicts

**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.

**Resend API + MCP.** `Idempotency-Key` on POST /emails and /emails/batch, kept for 24 hours. 106 MCP tools load at once, with no toolsets.

## Before you call either

### 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

### Resend API + MCP

1. Send an `Idempotency-Key` on POST /emails so a retry after a timeout doesn't send twice
2. Send a User-Agent header on raw HTTP calls or you'll get a 403
3. Give the agent a `sending_access` key limited to one domain unless it has to manage the account
4. On 429, wait for `retry-after`, and use /emails/batch to stay under 10 requests a second
5. Verify a domain before sending to anyone but your own address

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