Exchange 2010 - Disabled AD Accounts, how to hide the email addresses for accounts that have been disable due to user leaving company

Hello Experts ,

I hope you can help me.

In AD we have an OU which contains Disabled Accounts, these account are from users who have 

left the company, we need to retain these accounts for an extended period of time.

I need to hide the email address in exchange on those accounts because people still send emails to some of them.

Is there a way to do this.

Thanks in advance