Conditional Sections on Assistance Request Denied Message Template

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We require a contact to be in our system for a case to be created when they submit an email. If the contact does not exist the auto-response, Assistance Request Denied, is sent back. What I'd like to know is it possible to put a conditional section so that if they email say [email protected] that is sends one message and if they had emailed [email protected] they get a different message? Cases would still not be created.

We have multiple email addresses a customer can submit cases to and they all go to [email protected]