The out-of-office assistant can also be conveniently managed via the Exchange Management Shell, so if a user has forgotten to switch on the assistant before going on vacation...
Set-MailboxAutoReplyConfiguration frank -AutoReplyState Enabled -InternalMessage „Bin nicht da“ -ExternalMessage „Lieber Kunde ich komme bald wieder“
to switch off
Set-MailboxAutoReplyConfiguration frank -AutoReplyState Disabled
You could also build a nice template so that the company guidelines are adhered to, for example like this:
$internal = get-content d:\internal.html
$external = get-content d:\external.html
Set-MailboxAutoReplyConfiguration frank -AutoReplyState Enabled -InternalMessage „$internal“ -ExternalMessage „$external“
The HTML files can then be a nice template for the absence assistant, I think this one is quite nice:
(╯°□°）╯︵ ┻━┻ „I'M FREAKING OUT! WHERE IS FRAAANK???"
┬─┬ ノ( º _ ºノ) „Hey hey komm runter! Der ist am 30. April wieder da!!!“
I got from the Networkguy stolen 
