I have spent some time on trying to get shared mailboxes to work correctly. We want a solution so when an email is sent from a shared mailbox, the sent email goes into the shared mailbox sent folder, rather than the user’s sent folder.
For Office 365 there is a simple solution, but for Exchange* you might need a registry change which can be used for Office 2010, 2013 and 2016 .
*Microsoft Exchange Server 2013 Cumulative Update 9 or later or Microsoft Office 365 Exchange Online:
Cumulative Update 9 for Exchange Server 2013 introduced a new feature which allows administrators to configure the Sent Item folder to which a message is copied. Because this new feature is handled by the Exchange server, Outlook can be configured for online or cached Exchange mode. Please note that if you enable this feature and enable the DelegateSentItemsStyle registry value with a cached Outlook profile at the same time, two copies of the sent item will be saved in the shared mailboxes Sent Items folder.
The solution for Office 365 users
Navigate to the Shared mailbox in Office 365
Click on the Edit option under Sent items.
Under here you have the options to put a copy of the sent email in the shared mailbox sent items
The Solution for Exchange users
Be aware that you need to run this under the users profile, not as administrator.
Run regedit and navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook\Preferences
(The x.0 depends on your Outlook version: 16.0 = Outlook 2016, 15.0 = Outlook 2013 and 14.0 = Outlook 2010)
Create a new DWORD value.
Rename it DelegateSentItemsStyle
Set it to a value of 1
For a User Mailbox with “Send As” or “Send on behalf of”
There are 2 commands that can be run from Exchange Powershell against Exchange 2013/ 2016 or Office 365 to put a copy of any email “sent as” or “on behalf of” in that users sent items:
If the user has “Send As” permission against a mailbox use the following where the email address is the mailbox the user has permission to:
Set-Mailbox <email address> -MessageCopyForSentAsEnabled $true
If the user has “Send on Behalf of” permission against a mailbox use the following where the email address is the mailbox the user has permission to:
Set-Mailbox <email address> -MessageCopyForSendOnBehalfEnabled $true
I hope this helps and remember to backup your registry or PC before making changes to it.