Proxying non-ssl SMTP/POP to ssl SMTP/POP

[huynq]

Hi everyone,
I'm now using nginx in setting up a proxying mail system in my company. The
model is as below:

Mail client <=========> Nginx proxy <===========> Mail server

The stream between mail client and nginx is non-ssl connection (includes
smtp and pop3 stream), whereas the stream between nginx and mail server uses
ssl. The reason I use this model is that: I want to create a neutral node
that can modify the emails before being delivered to mail server or client.
However, I'm still stuck on the configuration of nginx to implement this
model. So if you have any idea about how to configure this system as well as
it's possibility with nginx, please help me. 

I'm still a newbie to this field, so if this is a dump question, please
forgive for my awkwardness.
Thank you very much!

Btw: I also referenced to the question of kgoj at :
http://forum.nginx.org/read.php?2,126528,126528#msg-126528. However, his
model is contrasted with my model and I haven't found any idea yet!

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,236390,236390#msg-236390