Enforce email mandatory TLS on incoming emails

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postfix discourages it. Quote Postfix Configuration Parameters

smtpd_tls_security_level

Mandatory TLS encryption: announce STARTTLS support to remote SMTP clients, and require that clients use TLS encryption. According to RFC 2487 this MUST NOT be applied in case of a publicly-referenced SMTP server. Instead, this option should be used only on dedicated servers.

I haven’t found any security blogs / advice setting postfix

smtpd_tls_security_level=encrypt

on search engines. Whonix.org would be the first one to do this.

There are two cases:

  • A) third-party servers that send e-mails to whonix.org that harden their security
  • B) those that don’t.

In case of A), incoming e-mail TLS encryption is already enforced through MTA-STS.
In case of B), well, if the servers that send e-mail to whonix.org don’t care about MTA-STS we might be able to force them to use TLS by switching that setting.

E-mail security generally is awful anyhow. A supported stronger patch so to speak is OpenPGP - Kicksecure.

Note:

  • This is only about the whonix.org server for incoming e-mails for Whonix team.
  • This isn’t about the Whonix software.
  • Whonix is not and does not aspire to become an e-mail service that offers services to users.
  • Receiving e-mail on whonix.org is only a very auxiliary project activity that I’ve assigned a very low priority given all other development work.
  • Private Communications Policy

For receiving e-mails, compatibility is more important than transport layer security because incoming e-mails might have legal importance.

For these reasons, I won’t implement this.

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