How do you mask assignee name in emails

Within our organization we support ~2000 external customers of a web based application. Because of this we currently do not use the customer portal; all communication goes through email.  When an email comes in, the incident is set  to a GROUP for both Owner and Assignee.  After assessing the issue it is assigned to a USER for that area of focus (sometimes developers).  When the USER responds their name is stamped within the email.  

Besides changing the USER last names to initials, is there a way to mask/hide the USERS name (possibly to the GROUP name) to prevent the customer from guessing the USERS email address and then emailing them directly?

Thanks for any recommendations,
Lowell Allen III