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Security

Encrypted mail gateway: automatic PGP, S/MIME fallback

TL;DR A transparent SMTP/IMAP proxy: encrypts for equipped correspondents, alerts otherwise.

18 Feb 2025 · Nicolas Albert

  • pgp
  • smime
  • email
  • gateway
Encrypted mail gateway: automatic PGP, S/MIME fallback

1 min read Reading 0%

A firm wants encrypted mail, but its clients won't generate a PGP key. CipherMail solves this by sitting between the mail client and the world: an SMTP/IMAP proxy that encrypts on the fly.

How it works

  • On send, we check whether the recipient has a public key in the directory.
  • If yes → the body is encrypted (PGP, or S/MIME if configured).
  • If not → the message goes in clear but raises a compliance alert on the admin side.

Why a proxy, not a new client

Adoption is the real lock. If the team must switch tools, the project dies. By staying transparent (standard IMAP/SMTP), CipherMail plugs in without training anyone.

Known limit

The weak link is still the correspondent who replies in clear. The proxy alerts, but doesn't force the other end — that isn't its job.

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