> On Feb 17, 2017, at 10:43 AM, Chris Green <c...@isbd.net> wrote: > > Ah, I've maybe just spotted the reason, smtp_tls_wrappermode is new in > postfix 3, is that what makes the difference?
Yes.
> I'd still like a simple explanation though! :-)
That's the simple explanation. SMTP directly over TLS requires the new
feature. TLS via the SMTP STARTTLS command dates back to Postfix 2.2
(and unofficial patches in even older Postfix versions).
--
Viktor.
