I am consistently getting smudges on envelopes, mostly on the leading edge, but occasionally on the trailing edge as well. I cleaned the heads, tried printing one envelope at a time or with several loaded and I still get smudges. If I replace the envelope with a piece of paper the same size, there's no problem, so I suspect it has to do with the thickness of the envelope vs regular paper. I tried printing on a different printer (Canon) and all is well, so that is my current solution....
Printing envelopes on Epson wf-3540 results in smudges
Printing envelopes on Epson wf-3540 results in smudges