If your source data is in Excel and has duplicates, run Power Query to remove those duplicates before running a Word mail merge.

How to Merge an Excel Spreadsheet Into Word Labels. The "Mail Merge" option in Microsoft Word is a powerful tool that you can use to merge Word documents with data stored in various databases ...

Master linking and embedding techniques to keep your Word documents updated with live Excel data effortlessly.

Link or Embed Data Open the Excel worksheet from which you want to extract data as well as the Word document into which you want to insert or embed the data.

In part three, you're finally ready to use the data you exported from Outlook to Excel, to create a mail merge with a Word document.