Failed to add data (error in send confirmation mail)

Failed to add data (error in send confirmation mail)

In these two last days e-mail notification does not work. Anything changed ??
The message error is the following: FAILED TO ADD DATA.
Furthermore, include user submitted data is blank. Is it a commn problem ?Please not that is urgent for my work to solve this problem....
I changed anything in the form at the voice SUCCESS - SEND CONFIRMATION MAIL.
Here it is the attachment.
Can you help me as soon as possible ?
Thanks !
I think the error is in the second field input.indirizzoemail....