Is it possible to update the acknowledgement email that is sent when a HR Helpdesk SR is created

When an individual sends an email to the HR Helpdesk, if that individual isnt recognised as an internal employee, the SR is created but without a contact. The individual is sent an acknowledgement email. I would like to update the standard text to remove this text:

Your service request can't be processed because a contact record couldn't be found for the email XXXX. If you have a contact record with a different email, provide the alternate email address by replying to this email.

and replace it with alternate text. How do I do this?