KB Article: http://support.microsoft.com/kb/2661294

INTRODUCTION

Consider the following scenario:

• You create some recipients by using Exchange Management Console or Exchange Management Shell in a Microsoft Exchange Server 2010 environment.
• The aliases of the recipients begin with one of the following combinations of lowercase characters followed by a hexadecimal number that has less than 5 digits:
  • sa
  • sb
  • sc

For example, the alias is sa000c1 or sbcc.

• You create an email address policy and apply the policy to the recipients.

In this scenario, the email address policy does not generate the email addresses of the recipients correctly. For example, the secondary email address of the recipients is not generated.