Outlook 2016 with a February 2016 update installed is downloading multiple messages. The recommendation is to revert to the previous build. See Outlook 2016 POP Account Problems for more information and instructions. (This is fixed in the March 2016 update.
Outlook users complain when Outlook downloads duplicate messages when they re-use Outlook data files. This is expected behavior when you use an old pst and leave mail on the server.
I moved my pst files to a new computer and set up Outlook to use the old pst files. When I try the first send/receive, Outlook downloads all of the emails off of the server even though I already have copies in the inbox. How do I get it to stop downloading the copies of the email? If I can't, how do I sort the email for the newly downloaded identical copies and delete them?
Duplicate remover utilities are available at Duplicate Remover Tools
You can't avoid Outlook downloading duplicates when you leave mail on the server. The "Mailbox Manager" file Outlook uses to keep track of messages that were downloaded is associated with the account that created it and downloaded the mail. When you create a new account, Outlook has to re-download all of the mail again.
There are ways to deal with this issue though:
1. Because POP3 only downloads mail that is in the Inbox, you can move the mail from the Inbox to another folder in your account online (log in using webmail) before taking Outlook online.
2. Let Outlook download the mail then add the Modified date field to the view, sort by it and delete all of the mail you just downloaded (that was previously downloaded.)
To add the Modified date field to the view and delete the duplicate messages:
- Close the Reading pane
- Right click on the row of field names and choose Field Chooser
- Select Date/Time fields from the drop down
- Drag Modified to the row of field names and drop it between two fields.
- Click on Modified to sort.
- Select the first message you downloaded in the session
- Scroll to the last (or last non-duplicate), hold Shift as you select the message
- Press Delete.
3. Turn off any rules you use and move the contents of the Inbox to a temporary folder. Download mail and delete the old mail from the Inbox. If you use Outlook 2007 or up, you don't need to move your mail our of the Inbox; you can choose a different folder as the delivery location in Account Settings, select account > Change folder.
4. You could use a duplicate remover tool to remove the duplicated messages. But honestly, that's not necessary.