---
title: "Sign or encrypt sensitive mail · Agent Wranglers"
url: https://agentwranglers.se/playbook/email/email-security/signed-encrypted-mail
updated: 2026-10-20
licence: "All rights reserved"
---

# Sign or encrypt sensitive mail

By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20.

- Level: Optional
- Chapter: [Email security](https://agentwranglers.se/playbook/email/email-security)
- Rule: For mail that must stay private or be provably yours, sign or encrypt it with S/MIME or OpenPGP.
- How: S/MIME needs a certificate from a trusted authority and works in most business mail apps. OpenPGP needs the recipient's public key. Both protect the message itself, not just the connection. For most apps, a link to a signed-in page is simpler.
- Check: Open a signed test message in a mail app such as Outlook or Thunderbird. It shows a valid signature from your address.

**For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers email playbook: https://agentwranglers.se/playbook/email/email-security/signed-encrypted-mail`.

- Previous: [Send no scripts or forms in email](https://agentwranglers.se/playbook/email/email-security/active-content)
- [Email security](https://agentwranglers.se/playbook/email/email-security)