On: Disabling SSLv3 and RC4

[cm2187]

Given gmail's volume that would pretty much make it a requirement for all other mail services. A mandatory STARSTTLS would make me happy!

[drdaeman → cm2187]

How mandatory STARTTLS (on Google servers' side) would help you against MitM downgrade attack?

The only way to avoid it is for your MUA to require STARTTLS.

[cm2187 → drdaeman]

Or for the server to terminate the connection if STARTTLS is not requested

[drdaeman → cm2187]

Yes, but how that'd prevent the attack?

The active attacker may tell your MUA to use the plain text, but this doesn't mean the whole connection must be unencrypted end-to-end. I don't see why the connection past the attacker can't still use STARTTLS (or even "classic" port-based TLS). Google servers won't even know the connection is not secured end-to-end.

That said, requiring TLS/STARTTLS on the server side is a good idea. But it doesn't protect from downgrade attacks.