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

Microsoft Excel is perhaps the most powerful spreadsheet application you can buy. But it also has some simple functions, like finding duplicates in data.

How can we find duplicate values across multiple columns? For this task, we’ll use two Excel helper formulas: One to concatenate the columns you’re comparing; a second to count the duplicates.

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.

How Can I Merge Two Columns of Data Using Microsoft Excel and Eliminate Duplicate Values?. There are two situations in which you might need to merge two columns of data in Excel 2013.