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OK, that explains why some users have multiple X500 addresses. Some as many as 5-6 all with different Administrative Group names. So, if a user is not migrated, there is really no need for them to have an X500 address, correct? Exchange will use the LegacyExchangeDN to deliver email.
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OK, that explains why some users have multiple X500 addresses. Some as many as 5-6 all with different Administrative Group names. So, if a user is not migrated, there is really no need for them to have an X500 address, correct? Exchange will use the LegacyExchangeDN to deliver email.

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Correct OSIExchange. X500 is only used if it is a Migrated account.
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Correct OSIExchange. X500 is only used if it is a Migrated account.

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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?
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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?

How does Exchange 2010 deliver internal emails?

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.