Any standard ESC/POS 80mm wide thermal receipt printer which presents as a serial port or raw print queue should work fine with PostalPoint. This includes most USB thermal receipt printers on the market, both name-brand ones and cheap Chinese clones.
If the horizontal bars on a printed receipt don't go all the way across, or they wrap to the next line, adjust the Receipt Width value in PostalPoint until it's just right. Start with 42 or 48, they're somewhat common values. This value can differ between printers, depending on what the printer's factory default font and font size is.
You can also configure PostalPoint to print receipts to your label printer if you don't have a receipt printer.