Zerosmtp MCP server

by msgwing·io.github.msgwing/zerosmtp·v1.0.2·5 stars

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

C69/100grade C

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Safety scan

C69/100

full report

Adoption

Growing

5 stars44 downloads/wk

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If you have run it, two minutes of your experience saves the next person an afternoon.

Zerosmtp tools (4)

write = sends, deletes, buys or posts

Read from the package source without running it. The installed server may list more.

check_device_oauth
Look up whether a printer, scanner, NAS or firewall has firmware
check_relay_reachable
Open a real TCP connection and TLS handshake to the relay from THIS
lookup_smtp_error
Identify a Microsoft 365 SMTP AUTH error string and say what it means,
relay_settings
The ZeroSMTP connection values, together with the two limits that decide

Public scan report

scanner v0.1.10 · 2026-10-29 · same rubric, same numbers if you re-run it

1 high

Code scan5 source files scanned25/25
–Live reliabilityno gateway calls yet and no remote to proben/a
–Tool poisoningtools not inspected (local package is not executed); not countedn/a
Auth qualitylocal package, no credentials required12/15
Maintenancerepository archived0/15
Maintainer identityregistry namespace matches repository owner; GitHub account older than a year8/10

Findings (1)

highRepository is archivedmaint.archived

Overall 69/100. Components that don't apply are left out of the denominator. Any critical finding is an F.Rubric Appeal a finding JSON

How Zerosmtp compares

Against every graded Email MCP server, from our own scans and uptime checks. Updated after each scan run.

Safety score: 69/100; higher than 36% of 916 Email servers
Tools: 4; the typical Email server has 7
Tools that change things: 0%; typical: 25%. Fewer write tools means less an agent can break
GitHub stars: 5; more than 82% of 493 Email servers
Downloads a week: 44; more than 30% of 235 Email servers with a package

What its tools let an agent do: 4 read

Install Zerosmtp in Claude Code, Cursor or VS Code

Runs npx -y zerosmtp-mcp on your machine. Read the scan report first; the gateway never runs local packages.

claude mcp add zerosmtp -- npx -y zerosmtp-mcp

Add to Cursor

What the publisher says

From the Zerosmtp repository's README, as published. We do not edit it. Read it on GitHub

Everything you need for the Microsoft 365 SMTP AUTH shutdown. Find out what breaks in your tenant, check whether your hardware has a way out, and keep it sending — including a free relay for the devices that will never speak OAuth. The relay is free with no paid tier, capped at 200 messages/day, and sends from a shared @msgwing.com address rather than your own (why).

Get a free account → · Exchange Online migration → · Documentation site · Quickstart · Code examples · FAQ · Deutsch · Polski

What's in here
Quickstart
Why ZeroSMTP?
⭐ Support ZeroSMTP
How does this compare to other options?
GitHub Actions
Code Examples
Security & Deliverability
Star History

### Arrived from the GitHub Marketplace?

This page is the README of the whole project, which is a free SMTP relay — so

the action you came for is below the fold. Here it is:

yaml

- uses: msgwing/ZeroSMTP@v1

with:

host: smtp.office365.com

cert-expiry-days: '14'

It checks outbound SMTP from the runner — ports, TLS, certificate and the

AUTH mechanisms offered — and **fails the job when the mail server's

certificate is inside the window you set**. Nobody watches a mail

certificate; it expires on a Sunday and the first report is somebody saying

scanning stopped working.

No install and no npm: the tool has no dependencies, so the action runs the

file shipped beside it. Every input, and the scheduled-canary setup that

reports without failing, is in GitHub Actions further

down.

What's in here

Shortened. The full README is on GitHub.

Nothing above is checked by us. What we check is on the safety report.

Grade history

2026-10-29downgradeA → Cscore 69: Repository is archived

Zerosmtp: common questions

Is Zerosmtp MCP server safe?: With care: it is graded C, so read the findings first (69/100). Read the Zerosmtp safety report
How do I install Zerosmtp?: It runs on your machine. Copy the Claude Code, Cursor, VS Code or Claude Desktop config from the install section.
Does Zerosmtp need an API key?: Not as far as the registry entry and our scan can tell: no credentials are declared or required.
Is Zerosmtp maintained?: The last commit was 18 days ago (2026-10-18). The latest release is v1.0.2.
What can I use instead of Zerosmtp?: Servers from other publishers that do the same job: Mailoo - Email MCP Server, three.ws Notifications MCP server and Imap MCP server.
How does Zerosmtp compare with other Email MCP servers?: safety score 69/100 (higher than 36% of 916 Email servers); tools 4 (the typical Email server has 7); tools that change things 0% (typical: 25%. Fewer write tools means less an agent can break). Full comparison.

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