We have Multiple mailboxes. Standard is when you send an email from those mailboxes, the emails are in your own send box. By adding this regkey it will be placed in the mailbox of where you send it from.
This is for Outlook 2010. Change 14.0 to the correct version. (Save the file as *.reg and run it)
Windows Registry Editor Version 5.00 [HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Preferences] "DelegateSentItemsStyle"=dword:00000001
14.0 = Office 2010
15.0 = Office 2013
16.0 = Office 2016