Exchange/Outlook: Emails sent as shared mailbox stored in Sent Items folder in my mailbox, Why?

Here is the setup. I have configured my mailbox in Outlook. I have added second mailbox to the same Outlook mail profile (usually a shared mailbox). I have send-as permissions on that shared mailbox. I sent email as the shared mailbox, those sent emails are freaking stored in Sent Items in MY MAILBOX. Why?

Because somebody in Microsoft thought that’s a GREAT idea. Or they think they can piss off lots of people. Exchange Devs!! You achieved your goal!

Microsoft explained about the Registry Key DelegateSentItemsStyle (at HERE) that you can make the Outlook to store the emails “send-as” shared mailbox to be stored in Shared Mailbox. Note to Microsoft: That must be the default setting.

If DelegateSentItemsStyle is 0 (default value), emails that sent-as shared mailbox WILL be stored in your mailbox. Value 1 is what we want that send-as emails store in “Sent Items” folder in Shared mailbox.

FIX: follow the instruction below to change the registry key

1. Exit Outlook.
2. Start Registry Editor. Press Windows Key+R to open a Run dialog box. Type regedit.exe and then press OK.
3. Locate and then select the following registry key: HKEY_CURRENT_USER\Software\Microsoft\Office\<x.0>\Outlook\Preferences
4. Select the DelegateSentItemsStyle value.
5. On the Edit menu, select Modify.
6. Type 1, and then select OK.
7. Exit Registry Editor.
8. Start Outlook.

Note on step 3: In this key path, the placeholder <x.0> represents 16.0 for Outlook 2016, Outlook for Office 365 and Outlook 2019.