Hi Sandeep,
If it is related to the error within the service invoked from the processing rule, you have to do as what HTH has indicated.
If it is related to the error in the document itself, you could create a new processing rule, place this as the first processing rule, and call the alert email here and not the standard email.
Alternatively, you could trap the exception event and send an error email. You could also try if putting the email address in the IS server helps you in all your cases. Else the alternative is to write your own service.
-Rajesh Rao
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