ZeroSMTP Check

Version updated for https://github.com/msgwing/ZeroSMTP to version v1.7.0.

• This action is used across all versions by 0 repositories.

Action Type

This is a Composite action.

Go to the GitHub Marketplace to find the latest changes.

Action Summary

This GitHub Action automates the process of auditing and managing Microsoft 365 SMTP AUTH shutdown. It helps identify exposed mailboxes, checks compatibility of devices with OAuth firmware, provides a free relay for backward compatibility, offers code examples and deployment recipes across multiple languages, and includes documentation on error messages and migration strategies.

What’s Changed

ZeroSMTP Check is now a GitHub Action, and the CLI explains what an SMTP error means rather than only whether the port is open.

The Action checks outbound SMTP from a runner and fails the job when the mail server’s certificate is inside a window you set. Nobody watches a mail certificate; it expires on a Sunday and the first report is somebody saying scanning stopped working.

- uses: msgwing/ZeroSMTP@v1.7.0
  with:
    host: smtp.office365.com
    cert-expiry-days: '14'

--explain takes the refusal your own client printed - a Postfix SASL line, a Python traceback, 1102 off a Kyocera panel, or the curl: (67) Login denied that shows none of the server’s answer at all. Fourteen error strings are covered, each with whether it can still be turned back on before the end of December 2026.

npx zerosmtp-check --explain "535 5.7.139 Authentication unsuccessful"

Port 25 is checked by default and goes first, because it is the one a provider is most likely to block.

Full notes in CHANGELOG.md.

• Msgwing
• GitHub Actions