220.127.116.11 Optimizing Send
When a messaging client sends a message in a client implementation of an optimization, the client can set the value of the PidTagTargetEntryId property (section 18.104.22.168) to the value of the PidTagEntryId property ([MS-OXCPERM] section 2.2.4) of the message being submitted. If this is done, the client moves the sent message to its local Sent Items folder after submission. Eventually, when the client imports its local Sent Mail folder changes to server, on the server side, the server can make use of the PidTagTargetEntryId property to optimize the operation by moving a copy of the submitted Message object to the Sent Items folder instead of requiring the client to upload the Message object content again. For more details about the server operation, see section 22.214.171.124.3.