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 Replace Duplicate Letters in Excel. Using the find and replace ability in Microsoft Excel 2010, you can quickly replace duplicate letters, words and cells in a spreadsheet document of any size.

How to Find & Replace Text Parts in MS Excel. Manually finding and replacing parts of text can be exceedingly tedious for lengthy Excel spreadsheets. Luckily, Microsoft included a couple of useful ...

You can do a mail merge in Microsoft Word and Excel to create personalized documents for many recipients at once.