Samsung ML 2550 - Manual (Page 81)

U SING P RINT M ATERIALS 4.18
3 When you print on labels, configure the paper source, type
and size properly in the software application. For details,
see page 5.7.
For details about setting on the control panel, see page 3.5.
4 After printing, close the Multi-Purpose Tray and the rear
output tray.
N OTE : To prevent labels from sticking, do not let the printed label
sheets stack up as they are printed out.