I need to re-iterate the bit about “In menu click File | Printer Settings… In window choose the printer. If you are using A4 paper then DL envelope is normal, for Letter then No 10 envelope. You need a margin of 12 mm (half inch) at the left and 24 mm (one inch) at the right. Having said that they are centred in the paper tray so should not print with an offset. Hi I have to say the manual for your printer is a bit unclear on which orientation to load the envelopes.
