Config Mail Proxy for POP3/SMTP microsoft exchange

[hcmnttan]

Thanks,
It works for me now. 
The error "550 5.7.1 Client does not have permissions to send as this
sender" is because our SMTP back-end did not accept SMTP relay from NGINX.
Configure SMTP backend allow NGINX relay fix my error.

I used xclient-> on, when I try to auth login, SMTP backend return error
with code "500 5.3.3 Unrecognized command" like my SMTP does not support
xclient ( I guess)

Thanks
Tan

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,243743,243879#msg-243879