Save Sent Items and Deleted Items for shared mailbox in correct folders

By default in Outlook when you send, or delete, messages from a shared mailbox the sent/deleted item goes into your own primary mailbox Sent Items / Deleted Items folders. Obviously this means no-one else with access to the shared mailbox can see what you have sent/deleted. To automatically place the sent or deleted messages into the corresponding folder in the shared mailbox you need to add a couple of registry entries on the client machine (note that this is on a per-user basis so would need to be applied to each user that logs on to any given PC – or you could simply push out the entries via GPO of course). In the Registry Editor (regedit.exe), add the following:

Sent Items
HKEY_CURRENT_USER\Software\Microsoft\Office\<x.0>\Outlook\Preferences
(16.0 = Office 2016, Office 2019, Office LTSC 2021, or Office 365, 15.0 = Office 2013, 14.0 = Office 2010)
Add a DWORD value: DelegateSentItemsStyle
Set Value to 1

Deleted Items
HKEY_CURRENT_USER\Software\Microsoft\Office\<x.0>\Outlook\Options\General
(16.0 = Office 2016, Office 2019, Office LTSC 2021, or Office 365, 15.0 = Office 2013, 14.0 = Office 2010)
Add a DWORD value: DelegateWastebasketStyle
Set Value to 4
(8 = Stores deleted items in your folder, 4 = Stores deleted items in the mailbox owner’s folder)