Digital Certificates – Case Sensitive

I am using Outlook 2011 on a MacBook Pro running version 10.9.1.

Whenever I receive digitally signed emails from anyone I get an error message that reads, "The e-mail address "*** Email address is removed for privacy ***" in the signing certificate does not match the sender's address."

I've determined that this happens probably because of a case mismatch with the email that is listed in the certificate and the actual email address that appears in the header of the mail message.  For example, I will see an email address like *** Email address is removed for privacy *** in the certificate.  But, his Exchange server translates the email address to *** Email address is removed for privacy ***.

Based on the RFC description for handling email, the Outlook 2011 client should accept mixed case.  But it doesn't seem to.

Is there a legitimate workaround to this?  I've looked for a setting to see if I can switch this behavior to match the RFC but I don't see one.

<grasping at straws> Can Microsoft put an item into the backlog to fix this please. </grasping at straws>

Thanks for your time.
John