Dirk St?cker:
> On Sun, 23 Feb 2014, Viktor Dukhovni wrote:
>
> >> I hope there aren't any TLS capable mailservers, which fallback to
> >> unencrypted transmission, when I use this.
> >
> > Fallback is up the client. I am not aware of any Internet facing
> > MX hosts that offer STARTTLS without any server certificate. Lots
> > of SMTP clients (not Postfix) don't support anonymous cipher-suites,
> > and such servers would have a lot of trouble receiving email.
>
> Sorry for unclear text. I meant not the host itself to fallback, but the
> client connecting to that host (like you describe).
When TLS is opportunistic but unusable, Postfix will certainly
deliver mail over a plaintext connection.
Wietse
