Contract - Signature Request Email Customization

We routinely send contracts to customers requesting e-signatures. Is there a way to customize and save the signature request email message? There is a pre-filled messages that says, "We kindly request you e-sign the document(s) at your earliest convenience. Your prompt attention is greatly appreciated. Thank you". I know there is a way to edit the email message for sales forms in Accounts and Settings but the 'contract' is not listed in the options dropdown. Please let me know if there is a way to edit and save a default email message for the signature request email in Contracts. Thank you.