Here are the multiple methods using which you can delete duplicate emails and items in Outlook and clean up your mailbox.

Free add-ons for Outlook and Thunderbird let you save all or selected e-mail attachments to a folder on your PC, and Yahoo Mail lets you download attachments in bulk—something you can't do ...

If you get Your Outlook data file cannot be configured error when opening Microsoft Outlook and your email account, see this post for the fixes.