Enable Automatic Replies for another user

Setting up Out-of-Office on behalf of another user

Via Exchange PowerShell

If you are an Exchange administrator, then using the Set-MailboxAutoReplyConfiguration Exchange PowerShell command is the supported and native way to go to enable Automatic Replies without logging on to the mailbox itself.

Syntax:

Set-MailboxAutoReplyConfiguration -Identity <username> -AutoReplyState Enabled -InternalMessage "Internal auto-reply message." -ExternalMessage "External auto-reply message."

tested in windows 10 client w office 2016, Exchange 2013 running on windows server 2012 R2 environment