I have a few users that still use Outlook 2000 in Corporate or Workgroup Mode with a service set up for Exchange. They use this mode since they need to share their calendar or access another's calendar. In addition they also have an Internet email account set up. It doesn't matter which order is used, e.g. Mailbox-user name or Internet email, results are the same. What happens is that when a user of Outlook 2000 CW sends an email and a recipient happens to be an Outlook Express user, the email never gets delivered. If that same Outlook 2000 CW user sends an email to an Outlook 2000 or Outlook 2003 user the email is delivered. Does anyone have any idea what's happening here?