On Tue, Jun 09, 2015 at 11:55:40AM -0500, Noel Jones wrote:
> Postfix isn't a proxy and can't be configured to behave as one.
> Maybe you're just using that term to refer to an email
> gateway/firewall, and not really expecting a proxy.
Admittedly it is possible to configure a degenerate installation
in which smtpd(8) proxies mail to another backend MTA without
queueing. I've used this for TLS termination in front of an MTA
with no TLS support.
http://www.postfix.org/SMTPD_PROXY_README.html
http://www.postfix.org/postconf.5.html#smtpd_proxy_filter
With care, one can abuse proxy handoff to insert Postfix in front
of another MTA. In such configurations one should generally
leave the proxy options parameter:
http://www.postfix.org/postconf.5.html#smtpd_proxy_options
empty to let the backend MTA reject invalid recipients, unless
Postfix has access to the recipient validation tables of the backend
MTA (in which case it may be OK to use "speed_adjust").
--
Viktor.
