AwoCoupon Email no work

hi, i have apply your plugin in my website but it no work:
I try test mode but plugin show me: Registration: Could not send test message: Non è stato possibile eseguire la funzione mail

I have set plugin with = Use default Joomla!: Yes
Can you help me?

Thanks

Can you set the processing start date earlier until it finds some orders? Just a hint, if you mouse over each field label it gives a more detailed description of what it is.