Outlook: How to save Sent Items in a Shared Mailbox
If you use Shared Mailboxes with Send As permissions emails sent from the Shared Mailbox end up in the user’s Sent Items rather than the Shared Mailbox’s Sent Item.
To change this behavior, you need to update your registry by running the following: DelegateSentItemsStyle.reg (right click the link and save the file).
*Please note, Outlook will also need to be configured to use Cached Exchange Mode:
On the File tab, click Account Settings, and then click Account Settings.
On the E-mail tab, select your Exchange Server account, click Change, and then enable the Use Cached Exchange Mode option.
Click Next, and then click Finish.
Exit and restart Outlook.