Customize Templates: Review the message templates associated with your DR campaign and ensure they are configured to utilize custom values effectively. The DR campaign out of the box uses custom values to set the message body.  Ensure that the templates facilitate how those custom values are filled out. 

Add Signature: If necessary, edit the templates to include the sender's signature at the end of the message body. This can be done by adding a custom value for the signature or directly incorporating it into the template.

Test Messages: Send test messages to verify that the templates are correctly configured to utilize custom values and include the signature where necessary.

Save Changes: Once you're satisfied with the customization, save your changes to apply them to your DR campaign.