Viktor Dukhovni: > > On 19 May 2021, at 3:07 pm, Wietse Venema <wie...@porcupine.org> wrote: > > > >> Server haproxy.example.com:587 accepts public connections and proxies to > >> submission.example.com:587 > >> Each server was given its own SSL cert (Let's Encrypt certbot). > > > > If the remote SMTP client negotiates a TLS handshake with > > haproxy.example.com:587, then that remote SMTP client will not > > negotiate a TLS handshake with submission.example.com:587. > > I haven't yet have cause to look closely at the Postfix "haproxy" code. > So I could be mistaken, but at first blush it appears that Postfix > handles the haproxy protocol *before* TLS, even in wrapper mode.
Haproxy can terminate TLS. Wietse > In which case the communication between haproxy and Postfix is always > in the clear. And especially on port 587 (STARTTLS, not wrapper mode) > the client will not initiate TLS until it gets through the initial ESMTP > greeting and EHLO exchanges. So there's no role for any possible certificates > on the haproxy side, it will remain a cleartext channel. > > With port 465, one might imagine haproxy terminating TLS, but it would then > still have to communicate with Postfix in the clear, and then re-establish > a new TLS connection, where it would be far simpler to just NOT terminate > TLS on the haproxy side, and then possibly leverage client certs when/if > desired, ... > > > So bottom line, the OPs use-case of TLS on both haproxy and Postfix does > not appear to make much sense... > > -- > Viktor. > >