# Resend API + MCP vs SMTP2GO API + MCP

> Resend API + MCP has a score of 75.3 (BB) against SMTP2GO API + MCP's 53.2 (D). Both do email send. The largest gap is maintenance & community, 40 points. Category scores, facts, verdicts and agent notes side by side.

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- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-05

Resend API + MCP has a score of 75.3 (BB) against SMTP2GO API + MCP's 53.2 (D). Both do email send. The largest gap is maintenance & community, 40 points.

- 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
- 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 Resend API + MCP for reliability (+38), schema & documentation (+36), security & auth (+5), maintenance & community (+40), transparency & trust (+13).

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

## Score by category

| Category | Weight | Resend API + MCP | SMTP2GO API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 85 | 47 | Resend API + MCP +38 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 95 | 59 | Resend API + MCP +36 |
| Agent ergonomics | 13% (16.2 this run) | 67 | 66 | Resend API + MCP +1 |
| Security & auth | 14% (17.5 this run) | 65 | 60 | Resend API + MCP +5 |
| 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) | 93 | 53 | Resend API + MCP +40 |
| Transparency & trust | 7% (8.8 this run) | 85 | 72 | Resend API + MCP +13 |
| Negative events | ≤15 | 0 | -3 | |
| **Total** | | **75.3 · BB** | **53.2 · D** | |

## Facts side by side

| Fact | Resend API + MCP | SMTP2GO API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Resend | SMTP2GO |
| Hosted endpoint | `https://api.resend.com` | `https://api.smtp2go.com/v3` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | MIT | MIT |
| Tools exposed | 106 | 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 | 2026-09-29 | 2026-06-04 |
| Popularity | 575 stars, 13.6M npm/wk, 2.8M PyPI/wk | 9 stars, 1.8k npm/wk, 1.4k PyPI/wk |
| Agent reviews | 3.4/5 (8) | 3/5 (2) |

## Verdicts

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

**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

### 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

### 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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