Mailer's Postmark Permit - cancel your mail as you want!

Cat maxicard, with a MPP postmark. I could have sent this through the mailstream, as I did with many other postcards/maxicards (without cover) to addresses in USA or abroad. The make-up postage was on the address side.

One unofficial alternative would be to work out an agreement with that postmaster and your mail carrier(s), to allow you to mail (or leave in your mailbox to be picked up/relayed, if you live in a "single, detached house") to him/her personally an envelope containing your pre-postmarked items, days in advance.
If that postmaster is reliable, then he could put your items into the mailstream exactly on the date they are pre-postmarked.
Of course, it's more reliable to go in-person, when possible.

Also, when you only need a philatelic cancel, not for real postal use, then you can do it yourself, at home.
Like this cat maxicard: I am not mailing it (although I could have). I am just creating a maxicard.

#MPP Herndon, VA 20170.