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

[Nguyen Huy]

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!
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