As a retired mailman, I will tell you now, that Christmas gratuities dictated the kind of service you got from me. I always did my job "properly, to the letter", however for the customers that were friendly,and appreciative there was service beyond. Things like instead of leaving a notice for you to go to the PO to pick up a package,I would put the package in the garage or back porch. . I would pay your postage dues out of my pocket. I would walk hold notices and change of addresses thru the system instead of tossing them into the lineup. If you didn't want the pennysaver,I would'nt leave one."A firing offense" I would make an extra effort to get to your snowed in mailbox, instead of refusing delivery as the regulations require.
It didn't even need to be a real tip,just simple things like conversations knowing my name, asking about my family. In other words,make yourself a person to me and not just a mailbox.