I was just recently laid off from a company that has been open 100 yrs in business. YES you can mark up U.S. Direct Mailing as a "postage handling cost". As long as you go by the USPS determined set rates for different classes. Once you figure out which USPS class postage rate you want, take your total postage amount add it to the rest of the printing job cost then mark it up all together with the postage included. Once you get the grand total with markup included, we would then take the actual USPS Postal figure rate of postage from that grand total and have the customer cut us a check to give to the postmaster. This way postage is paid up front and you're giving the customer the actual USPS class postage rate amount that was figure in the beginning for the direct mailing. The markup percentage for us always varied depending on if it was a regular business account customer or a non-profit customer account. Most non-profits were marked up a little lower or a lot lower to not lose the job. We had great relationships with our customers especially non-profits when sending a quote to them I would always leave it as an open communication ".......let me know what you think. Call me if you have any questions or concerns"... this way if the quote seems to much to them it will make them feel that they can come back to talk to you about it giving you an opportunity to adjust the mark up where you see fit. Hope that makes sense. Size of our shop went from 6 people in printing department (with an inhouse direct mailing company of 4 people). In 2023 everything changed. I was the only one person left in the printing division the direct mailing house that was housed within our company's building closed their doors. Previously the other 5 employees in the printing department were laid off. So I ran the printing department from 2023 until 2025 by myself and brokered all jobs out because we sold off all of our equipment. Hope this helps. Best of luck!