Also, the "Active Directory Clean-up Wizard" adds the old X500 address to the merged user object.

(For those who have not used the ADCW, ADCW merges the Active Directory Connector-created disabled user accounts or contacts that correspond to an Exchange 5.5 mailbox with the AD user that owns the Ex5.5 mailbox.)

Thats an excellent point Peter. I was thinking more in the mindset that the ADC wasn't used--but thanks for the addition.