Unable to determine RCTI message status via ERS

Hi All,

In my system ERS output type has been configured to sent mail to vendor for RCTI in respect to PO line item. Now the problem is mail is sent via ERS for RCTI but vendor did not received the mail for a particular line item where the GR nd IR been done. Is there any place where we can check if the mail sent to particular vendor sent successfully or not. Is there any indicator to determine that from PO?

Thanks & Regards