update to apply messagecopyforsentasenabled to any type of mailbox in exchange server 2016
This update describes a change in which the MessageCopyForSentAsEnabled and messagecopyforsendonbehalfenabled settings to save sent messages into a different mailbox can be applied to any type of mailbox with the Set-Mailbox cmdlet, not just shared mailboxes. This feature keeps a copy of the email in the Sent Items folder of the alternative mailbox.
Install Cumulative Update 4 for exchange server 2016 or a later cumulative update for Exchange Server 2016.