Hello,
I'm not familiar with mail merge, so if I'm off topic please ignore, but I can help to create a unique list in excel. Assuming that names are in column A use :: =IF(COUNTIF($A$1:A1,A1)>1,"",ROW()) in b1 and :: =IFERROR(INDEX($A:$A,MATCH(SMALL(B:B,ROW()),$B:$B)),"") in c1 and drag down. This will give you a unique list in column C.
Hope this helps,
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