what version of word?
A few years ago I used to mail out a monthly letter.
an excel list of addresses printing a page layout for use in a windowed envelope.
not identical but I seem to remember that I used the wizard to set up the fields ... and the only things that ever went wrong was jammed paper .... and not enough paper.
but you are using labels .... I don't see that it should be a problem .... unless you are using an inkjet printer with a print area which is smaller than the label area.
(the top margin is generally a few mm but the bottom margin can be anything up to 2.5cm which is half a label)