Those postage machines are still around, in offices all across the country.
Hubby and I talked about this possibility, the day PA announced their postmark nonsense.
OK, thanks... I thought maybe laser printers etc. caused these not to be needed any more. But yes, a postmark is not something that has any precautions to prevent forgery. And at least where we are at the ballot return envelopes say “no postage necessary” on them. All you need is a hand stamp and you could put whatever post mark you want on your return envelope. You could probably carve one that would pass muster out of a potato if you knew what you were doing.
The voting procedures set up are insecure and depend on the "honor system".