On 2013-08-06 19:35, OLIVER Patrice wrote:

I cannot continue with rcpt to syntax and I have the following message :
rcpt to:530 5.7.1 Client was not authenticated

[cut]

Does anyone have an idea ?

Sure: https://en.wikipedia.org/wiki/SMTP_Authentication

In other words: stunnel worked fine and there is nothing you can do with stunnel to deal with your problem.

Mike