Making Nice at the Local Post Office

Mailing out manuscripts is WAY cheaper via Media Mail-- but getting the P.O. to cooperate may be difficult. The "bound or unbound?" question is alive and important. My experience is like that of other writers who have wrestled with it: my post office did not recognize Media Mail or help me with it. But once we had the printed regulations in hand we talked it through together, and both bound and loose leaf script MS are now accepted cheerfully by them. When the clerks see me in line they get out the "Media Mail" rubber stamp! "Unbound" is important to novelists and "long short story" writers besides us, and I've had this conversation with them. Entire POs seem to come to an attitude: either writers are pets to be enjoyed and encouraged, or they are dangerous freeloaders who should be resisted and harassed! Going an extra mile to a PO where you can get the clerks to be helpful rather than hostile may be worth the effort....
My PO recently told me that the new self-serve machine won't do Media Mail. Now I'm wondering whether this is true or if they just want me to stand in line? I do stand in line-- I've never tried going up to the back window and handing the stamped package in. I do hand it to the PO truck driver some times, or leave it in my house mailbox if I'm sure the regular carrier is working......