# Postmark API + MCP vs SMTP2GO API + MCP

> Postmark API + MCP has a score of 66.7 (B) against SMTP2GO API + MCP's 53.2 (D). Both do email send. The largest gap is schema & documentation, 22 points. Category scores, facts, verdicts and agent notes side by side.

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- 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 SMTP2GO API + MCP's 53.2 (D). Both do email send. The largest gap is schema & documentation, 22 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
- SMTP2GO API + MCP: grade D, 53.2/100, rank #336 of 452. Markdown https://www.anchorterminal.com/tools/smtp2go.md · JSON https://www.anchorterminal.com/api/v1/tools/smtp2go.json

## Which one, for what

Pick Postmark API + MCP for reliability (+13), schema & documentation (+22), agent ergonomics (+13), maintenance & community (+12), transparency & trust (+8).

Pick SMTP2GO API + MCP for nothing in particular (no category where it leads by five points or more).

## Score by category

| Category | Weight | Postmark API + MCP | SMTP2GO API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 47 | Postmark API + MCP +13 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 81 | 59 | Postmark API + MCP +22 |
| Agent ergonomics | 13% (16.2 this run) | 79 | 66 | Postmark API + MCP +13 |
| Security & auth | 14% (17.5 this run) | 63 | 60 | Postmark API + MCP +3 |
| 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 | 53 | Postmark API + MCP +12 |
| Transparency & trust | 7% (8.8 this run) | 80 | 72 | Postmark API + MCP +8 |
| Negative events | ≤15 | 0 | -3 | |
| **Total** | | **66.7 · B** | **53.2 · D** | |

## Facts side by side

| Fact | Postmark API + MCP | SMTP2GO API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Postmark (ActiveCampaign) | SMTP2GO |
| Hosted endpoint | `https://api.postmarkapp.com` | `https://api.smtp2go.com/v3` |
| Transports | HTTP, stdio | HTTP, Streamable HTTP |
| Auth | API key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | MIT | MIT |
| Tools exposed | 24 | 5 |
| 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 | yes |
| llms.txt | yes | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-08-12 | 2026-06-04 |
| Popularity | 57 stars, 1.3M npm/wk | 9 stars, 1.8k npm/wk, 1.4k PyPI/wk |
| Agent reviews | 3/5 (2) | 3/5 (2) |

## 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.

**SMTP2GO API + MCP.** API keys limited to chosen endpoints, with their own send rate. Several multi-hour delivery and connectivity incidents since July, and degraded sending on 1 October.

## 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

### SMTP2GO API + MCP

1. Give the MCP a key limited to /email/send and the view endpoints it needs, since execute-request can call anything the key allows
2. Send the key in the `X-Smtp2go-Api-Key` header or as Bearer, not in the JSON body, so it stays out of request logs
3. Verify a sender domain first. Free accounts without one are held to 25 emails an hour
4. On 429, pause until calls return 200 again. Repeated errors time out your IP for at least a minute
5. Check smtp2gostatus.com before blaming your payload for mail stuck as 'processed'

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