Is it possible to change the host name when customizing email notifications in OEM?

I need to change the value for the "Host" filed in a default email notification to obsfucate the actual DNS name for the Host. I have looked through the documentation for "Email Customization" and do not find anything that would work.

What I would like to do is to substitute a string for the host name field depending upon the value in the field. Thus, if the HOST_NAME attribute value is xyz.abc.com, I would ideally like to create a lookup table for a one-to-one substitution. Less elegantly, I would settle for a CASE expression dependent upon the value for HOST_NAME.