Hello,

By default, with Office 365 ProPlus (2013 and 2016 for sure), when you send/delete a mail from a shared mailbox on which you have delegation on it, those items go into your ‘Sent Items’ and ‘Deleted Items’ in your mailbox, and not in the delegate’s one.

This is editable, indeed, for a better collaboration, you may want to store those mails in the shared mailbox, for everyone to see them. You have two solutions to do this, you can do it manually for one computer with two registry keys, or you can create a GPO to target a lot more computers.

Sent Office 365 Deleted Item Shared Mailbox – Manual Registry Keys

To do that, you need to tweak those two registry keys :

#Sent
New-ItemProperty -Path HKCU:\Software\Microsoft\Office15.0\Outlook\Preferences -Name DelegateSentItemsStyle -PropertyType DWORD -Value 1 -Force
#Deleted
New-ItemProperty -Path HKCU:\Software\Microsoft\Office15.0\Outlook\Options\General -Name DelegateWastebasketStyle -PropertyType DWORD -Value 4 -Force

Sent Office 365 Deleted Item Shared Mailbox – GPO

You can also deploy the deleted items setting by GPO :

Sent Office 365 Deleted Item Shared Mailbox – Complete GPO

To get the Outlook settings in your GPO, you need the Office ADMX files, you can download them for each version from Microsoft :

• Office 2013 : https://www.microsoft.com/en-us/download/details.aspx?id=35554
• Office 2016 : https://www.microsoft.com/en-us/download/details.aspx?id=49030

Note : It works with other version of Outlook, you just need to change the version number in the path :

• Outlook 2003 : 11.0
• Outlook 2007 : 12.0
• Outlook 2010 : 14.0
• Outlook 2013 : 15.0
• Outlook 2016 : 16.0