This gave me an idea: what do people think about an ESMTP extension that enforces TLS?
MTA1 ----------> MTA2 ---------> MTA3 TLS TLS with the idea of having an X-header that basically says "do not forward if no TLS available" so MTA1 sends to MTA2 encrypted. MTA2 reads that header and says EHLO to MTA3. If MTA3 does not reply with TLS, MTA2 retunrs an NDR to MTA1 with "could not deliver, TLS not available". The big problem that I see is backward compatibility - one would need a ehlo flag that signifies this capability in order to enable MTA1 not to send to MTA2 if MTA2 was not able to recognize the header. cheers Bernhard ----------------original message----------------- From: "martijn.list" martijn.l...@gmail.com To: postfix-users@postfix.org Date: Fri, 25 Feb 2011 09:27:36 +0100 ------------------------------------------------- > On 02/25/2011 09:02 AM, Nicolas Michel wrote: >> Hello, >> >> I was asking myself about the kind of connection used by a MTA to >> contact another one. >> For exemple, I know that we can setup in a MUA an SSL (or TLS) >> connection when configuring the SMTP connection. So the connection >> between the MUA and the MTA is encrypted. >> >> But can we configure postfix in some way to ask by default an encrypted >> connection when sending mail to others MTA? Or maybe it already do it by >> default? >> >> So we may have something like that : >> >> MUA -----------> MTA -----------> MTA ------------> MUA >> encrypted encrypted encrypted >> >> I know we can't guarantee that the entire flow will be encrypted because >> we only have control on our MTA. >> >> But is it possible? > > If the other MTAs are not under your control, you cannot enforce TLS > between the other MTAs. You can only enforce TLS between the MTA you > control and first MTA it connects to. After that you are no longer in > control. > > Kind regards, > > Martijn Brinkers > -- ------------- Bernhard Rohrer Consulting 529 Howth Road Dublin 5, Ireland +353 87 7907 134
