After a long time, I have opened Outlook 2016. I saw surprised all mails including inbox, outbox have created another copy of the email. Every mail has two copy in Outlook. I have removed many duplicate emails manually. But it’s not possible to delete above 1000+ emails. Then, I have tried to search this problem over your forum and find below thread. But it’s not helpful for me.

portal.smartertools.com/community/a2479/duplicate-emails.aspx

I need your help to opt the best resource which will remove duplicate emails in Outlook.