nginx as smtp proxy

[Buzzz]

> Hello!
>
> Note however that after authentication nginx establishes opaque
> pipe between client and backend, so everything client sends will
> be transferred to backend (and vice versa).  So if *client*
> re-sends authentication for some reason - this will be seen by
> backend.
>
> Maxim Dounin
>
>
The problem was the backend smtp server that does not support the xclient
command issued by nginx.

I've disabled the command and now works properly

Thx for help,
Davide