I'm trying to print a priority mail label (4.25x5.5) on my iMac with MS Word 2016 for Mac on a Brother MFC-L2740DW printer. Trouble is, this doesn't work as it did for me in Windows. When I feed the label through the paper tray, back cover open, the label prints as if it were an 8.5x11 page. In Windows, I'd feed the label through, centered in the manual feed slot paper guides, and it would print just fine. In Mac, I have to align the label as best I can against the left paper guide. The printer user manual says that the Brother printer driver window will appear after using Word's printer command, but that doesn't happen in Mac. What am I doing wrong? Thanks.