# io.github.msgwing/zerosmtp (npm · zerosmtp-mcp)

A free SMTP relay that still takes a username and password, for devices that cannot do OAuth 2.0.

- Trust score: 87/100 (high trust)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-09-20

## Components

- npm · `zerosmtp-mcp`: 87/100 (this document), [markdown](https://verifymcp.io/servers/msgwing-zerosmtp/zerosmtp-mcp.md), [page](https://verifymcp.io/servers/msgwing-zerosmtp/zerosmtp-mcp)

## Channel facts

- Registry: `npm`
- Package: `zerosmtp-mcp`
- Version: `1.0.2`
- Transport: `stdio`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically from public evidence about the published package, including repeated runs of it in an isolated sandbox, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-09-20.

- **Supply Chain Security**: 100/100
  - No malware found by supply-chain analysis.
  - No known CVEs affecting this package version or its production dependencies.
  - No install/post-install scripts declared.
  - No production dependencies, so there is no dependency health to assess.
- **Provenance & Transparency**: 100/100
  - Source repository is publicly reachable at the declared URL.
  - Cryptographically verified build provenance (signed, bound to msgwing/ZeroSMTP).
  - Clear OSI-approved license (MIT).
  - Actively maintained (last published 18 days ago).
  - Publishes a security disclosure policy (SECURITY.md).
- **Schema Quality & AI Usability**: 74/100
  - AI-judged instruction clarity (good).
  - Tool/resource definitions use about 362 tokens (~90/item across 4 items; 4 tools + 0 resources), lean.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 63/100
  - Stability observed for 19 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 4 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 5 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 20/100
  - Spec-recency check failed: implements MCP spec 2024-11-05; the latest is 2026-07-28.

## Install

### How do I install the io.github.msgwing/zerosmtp MCP server?

io.github.msgwing/zerosmtp runs locally as an npm package, launched with npx -y zerosmtp-mcp. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add msgwing-zerosmtp -- npx -y zerosmtp-mcp
```

### Cursor

```json
{
  "mcpServers": {
    "msgwing-zerosmtp": {
      "command": "npx",
      "args": [
        "-y",
        "zerosmtp-mcp"
      ]
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "msgwing-zerosmtp": {
      "command": "npx",
      "args": [
        "-y",
        "zerosmtp-mcp"
      ]
    }
  }
}
```

### Codex

```bash
codex mcp add msgwing-zerosmtp -- npx -y zerosmtp-mcp
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "msgwing-zerosmtp": {
      "type": "local",
      "command": [
        "npx",
        "-y",
        "zerosmtp-mcp"
      ],
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add msgwing-zerosmtp --command npx --arg -y --arg zerosmtp-mcp
```

### Hermes

```yaml
mcp_servers:
  msgwing-zerosmtp:
    command: "npx"
    args: ["-y", "zerosmtp-mcp"]
```

### Netclaw

```json
{
  "McpServers": {
    "msgwing-zerosmtp": {
      "Transport": "stdio",
      "Command": "npx",
      "Arguments": [
        "-y",
        "zerosmtp-mcp"
      ]
    }
  }
}
```

### Vellum

```bash
assistant mcp add msgwing-zerosmtp -t stdio -c npx -a -y zerosmtp-mcp
```

### Other

```json
{
  "mcpServers": {
    "msgwing-zerosmtp": {
      "command": "npx",
      "args": [
        "-y",
        "zerosmtp-mcp"
      ]
    }
  }
}
```

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-09-19 (score 87, +1)

No change was recorded against any check on this day. Stability & Change Management went from 57 to 60. That category is still filling its 30-day observation window: 17 days of observed history at the previous scan, 18 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-17 (score 86, +1)

No change was recorded against any check on this day. Stability & Change Management went from 50 to 53. That category is still filling its 30-day observation window: 15 days of observed history at the previous scan, 16 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-15 (score 85, +1)

No change was recorded against any check on this day. Stability & Change Management went from 43 to 47. That category is still filling its 30-day observation window: 13 days of observed history at the previous scan, 14 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-13 (score 84, +1)

No change was recorded against any check on this day. Stability & Change Management went from 37 to 40. That category is still filling its 30-day observation window: 11 days of observed history at the previous scan, 12 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-11 (score 83, +1)

No change was recorded against any check on this day. Stability & Change Management went from 30 to 33. That category is still filling its 30-day observation window: 9 days of observed history at the previous scan, 10 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-09 (score 82, +4)

- [functional improvement] Stability: unverified → 0.27

### 2026-09-01 (score 78)

First indexed and scored.

## MCP tools (4)

### `lookup_smtp_error` (~63 tokens)

Identify a Microsoft 365 SMTP AUTH error string and say what it means, what caused it, and whether an administrator can still undo the cause. Paste the line the server or the mail library printed.

Input parameters:

- `text` (string, required): The error string, as printed.

### `check_device_oauth` (~82 tokens)

Look up whether a printer, scanner, NAS or firewall has firmware supporting OAuth 2.0 for SMTP, according to the vendor's own published statement. Answers "must this device be replaced or relayed".

Input parameters:

- `model` (string): Optional model or series.
- `vendor` (string, required): Vendor, e.g. Canon, Ricoh, Synology.

### `relay_settings` (~36 tokens)

The ZeroSMTP connection values, together with the two limits that decide whether it is the right answer at all. Returns both without being asked.

### `check_relay_reachable` (~93 tokens)

Open a real TCP connection and TLS handshake to the relay from THIS machine's network and report what happened. Sends no credentials and no mail. This is the one question documentation cannot answer: whether the firewall in front of the asker permits outbound 587.

Input parameters:

- `host` (string): Host, defaults to mx.msgwing.com.
- `port` (number): Port, 587 (default) or 465.

## Diagnostics

Captured diagnostic sections: Provenance, Dependencies. The full working is on the page: https://verifymcp.io/servers/msgwing-zerosmtp/zerosmtp-mcp#diagnostics

## Score history

- 2026-09-20: 87
- 2026-09-19: 87
- 2026-09-18: 86
- 2026-09-17: 86
- 2026-09-16: 85
- 2026-09-15: 85
- 2026-09-14: 84
- 2026-09-13: 84
- 2026-09-12: 83
- 2026-09-11: 83
- 2026-09-10: 82
- 2026-09-09: 82
- 2026-09-08: 78
- 2026-09-07: 78
- 2026-09-06: 78
- 2026-09-05: 78
- 2026-09-04: 78
- 2026-09-03: 78
- 2026-09-02: 78
- 2026-09-01: 78

## Common questions

### What is the io.github.msgwing/zerosmtp MCP server?

io.github.msgwing/zerosmtp is an MCP server listed in the public MCP registry as io.github.msgwing/zerosmtp. A free SMTP relay that still takes a username and password, for devices that cannot do OAuth 2.0. This page covers its npm package (zerosmtp-mcp).

### Is the io.github.msgwing/zerosmtp MCP server safe to use?

io.github.msgwing/zerosmtp scores 87 out of 100 on VerifyMCP. We found no known CVEs affecting it as of 20 September 2026. It declares no install or post-install scripts. Its build provenance is signed and verified. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the io.github.msgwing/zerosmtp MCP server expose?

io.github.msgwing/zerosmtp exposes 4 tools: lookup_smtp_error, check_device_oauth, relay_settings, check_relay_reachable. Their descriptions and schemas cost roughly 274 tokens of context every time the server is loaded.

### Is the io.github.msgwing/zerosmtp MCP server still maintained?

io.github.msgwing/zerosmtp is still listed as active in the MCP registry. We last reached this channel on 20 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

### What licence is the io.github.msgwing/zerosmtp MCP server under?

io.github.msgwing/zerosmtp declares the MIT licence, which is OSI-approved. That covers the source only, and says nothing about the cost of any service it calls.

## Links

- npm package: https://www.npmjs.com/package/zerosmtp-mcp
- Socket report: https://socket.dev/npm/package/zerosmtp-mcp
- Repository: https://github.com/msgwing/ZeroSMTP
- Changelog RSS feed: https://verifymcp.io/servers/msgwing-zerosmtp/zerosmtp-mcp.xml
- Changelog JSON feed: https://verifymcp.io/servers/msgwing-zerosmtp/zerosmtp-mcp.json
- HTML version of this page: https://verifymcp.io/servers/msgwing-zerosmtp/zerosmtp-mcp