I know the answer to this is probably somewhere on this forum but my situation may be unique so I will ask. I know SMTP is only used for Internet bound emails. I know Outlook cache uses X500 addresses. Does Exchange 2010 use X500 exclusively for internal email? Reason I ask is not everyone has an X500 address. In fact, when I create a new mailbox from scratch using the Console, it does not create an X500 address, only an X400 address. I know everyone has a LegacyExchangeDN value regardless so my question I guess is does Exchange use X500 when its available and resort to LegacyExchangeDN (which is the same value) if the X500 address is not there?