nginx as smtp proxy
i am here to ask help about how to configure Nginx as a reverse proxy for POP3/SMTP service. We have a Zimbra server offering services as webmail, POP/SMTP, Calendar, etc. The Zimbra server inside the LAN provides all ok.
After that, i configured an Apache2 as a reverse proxy on DMZ to provide WebMail through HTTPs to external clients. It redirects to Zimbra server on LAN. It all worked ok.
The issue i am facing now is how to provide also POP3/SMTP/POP3SSL/SMTPSSL/TLS service to external clients through a reverse proxy. Apache2 doesn't provide this capabilities, and Nginx community doesn't provide any kind of tutorials, wikis or documents where i can approach a solution.
i would be very grateful is somebody could send me some doc or tip.
thank you in advance.