Not according to dovecot doco ... from https://wiki2.dovecot.org/PasswordDatabase/ExtraFields/Proxy
*NOTE: LMTP/doveadm proxying doesn't support SSL/TLS currently - any ssl/starttls extra field is ignored *rgds Matt > Tobi <mailto:tobiswo...@gmail.com> > 23 November 2017 at 6:31 pm > Hi > > I got dovecot 2.2.26 on a Centos7 with latest updates. Dovecot is > configured to act as director and delivers to my two backend servers. > I enabled lmtp proxy on director to listen on port 24. > > Now I see in msg headers that the connection to the lmtp proxy uses > STARTTLS but the connection from proxy to backend seems to be > unencrypted. Is it possible to enforce the use of STARTTLS in the > connection from the director to the backend as well? > > Regards > > tobi
