Here is a useful Powershell Script for fixing X500 Email address issues on Exchange boxen…
Useful Script: Missing X500 Email Addresses (IMCEAEX Errors)
Alert - Archived Data
Please note that the old Network Blog content (from http://www.networkblog.net) is included for historic purposes only. Much of this data is either no longer relevant or may be missing from the original source. Most of this data was back from my MVP age and is over ten years old. Thus, many of the links are no longer valid as Microsoft has changed the links on many of their Technet sites.