Alert Error

Hi Experts,

I am doing File to IDoc. I want to trigger Alert by sending E-mail, when ever any error occur in the Scenario. I have done the Alert configuration. When an error is occured Alert is not Triggering. i checked in the log, it is displaying error "BCS exception (DNS_SREQ) occurred". what will be the problem? Can any one please help me out.

Regards

Venkatesh