2.2.3.2 Exchange Distinguished Name
The legacyExchangeDN attribute represents a distinguished name (DN) of the entry. This DN MUST be formatted as specified in [MS-OXOABK] section 2.2.1.1. This value MAY<4> be used as a proxy address for an entry, with the following format.
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proxyAddressFromExchangeDN ::= "EX:" <Exchange DN> <Exchange DN> ::= ; The value of the LDAP attribute legacyExchangeDN