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!