2.2.2 [RFC3501] Section 2.2.2, Server Protocol Sender and Client Protocol Receiver
The specification states: "Server data MAY be sent as a result of a client command, or MAY be sent unilaterally by the server."
Microsoft Exchange Server 2007, Microsoft Exchange Server 2010, Microsoft Exchange Server 2013
Microsoft Exchange Server sends data to the client unilaterally.
The specification states: "Servers SHOULD enforce the syntax outlined in this specification strictly. Any client command with a protocol syntax error, including (but not limited to) missing or extraneous spaces or arguments, SHOULD be rejected, and the client given a BAD server completion response."
Exchange 2007, Exchange 2010, Exchange 2013
Microsoft Exchange is liberal in parsing the spaces in commands. For more details, see section 2.1.6 in this document.