On Fri, 2014-08-08 at 15:36 +0200, Reindl Harald wrote:
Am 08.08.2014 um 15:21 schrieb Nikos Mavrogiannopoulos:
Postfix is a different kind of beast though. It does not typically use TLS, but uses some kind of opportunistic security that allows anonymous ciphersuites. So it's a bit hard to enforce anything there, as man-in-the-middle attacks are possible by design
and keep in mind in case of opportunistic TLS if you restrict ciphers and the SMTP client don't support what you offer it falls back to completly plaintext which defeats the intention
[...]
in short: MTA's acting as public MX must not enforce default TLS policies from the distribution shipping the package
Not really. I'd expect a mail server to always connect with TLS to servers that it has previously connected with TLS to. Otherwise I could always see the plaintext messages by blocking any TLS communication. Nevertheless, this is application policy, and the system policy does not apply here.
regards, Nikos