Report Server Subscription Configuration ISSUE

I Have Created A Subscription in our Development Server With below Steps.

1)Opened Report Configuration Manager and Configure Email Settings. 2) Opened Report Manager and configured a Report Data source with Store credentials, which is my domain login account and able to use same to connection to database engine. 3) Went to Subscription tab in that report and configured Subscription with schedule.

Error on "Status" bar of Subscription tab : Failure sending mail: The report server has encountered a configuration error. Mail will not be resent.

Checked log

1st time shot - Throwing Microsoft.ReportingServices.Diagnostics.Utilities.OperationNotSupportedNativeModeException: , Microsoft.ReportingServices.Diagnostics.Utilities.OperationNotSupportedNativeModeException: This operation is not supported on a report server that runs in native mode.;

2nd time Shot - Throwing Microsoft.ReportingServices.Diagnostics.Utilities.ServerConfigurationErrorException: AuthzInitializeContextFromSid: Win32 error: 5; possible reason - service account doesn't have rights to check domain user SIDs., Microsoft.ReportingServices.Diagnostics.Utilities.ServerConfigurationErrorException: The report server has encountered a configuration error. ;

Questions-

1) How check "reporting server window Service has Send AS permission on SMTP Server"? (Does it means to say that reporting server service account should has such permission?).

2) Any specific reason for first and second error?