They don't have postmarks since they're pre-paid business mail so they have a permit # instead in the corner that the post office uses to charge them for postage. Although that could happen I guess when you think about it that could happen with any bill in the mail since they mail them all that way. I've always gotten my credit card bills promptly after the closing dates. Plus as long as you have a decent grace period there's no interest to incur.
One thing I did NOT get on time was my last voting ballot! They mailed a form I had to send back in order to get my absentee ballot mailed. I got that ON the day the form was supposed to have already been received back via mail. There was no way for me to vote. Interestingly there were a lot of anti-renters propositions on the ballet and people like me that live in apartments were the ones not getting our forms in time.
Everything passed how I wanted it to though so it turned out okay.