The very useful addon Postal should be added to the addon bundle, that can be downloaded here: https://www.wow-mania.com/downloads
The (running/tested) addon can be downloaded here:
https://legacy-wow.com/wotlk-addons/postal/

I used the recommendet Auctioneer version from the our Addon Pack "Addons for WotLK (61 addons)" https://www.wow-mania.com/downloads , but It isn´t working eitherway. The problem is when i try to post a item either under Appraiser/Post it gives me this message: "Unable to confirm auction for [whatev...

I got it. You have to make sure, that you don´t have too many sub-directorys.
The [Addon-name].toc has to be in the first level of the addon folder, example:
wrong:
Interface/AddOns/recount r6439/Recount/Recount.toc

right:
Interface/AddOns/Recount/Recount.toc

I got the same problem.
I also put them in Interface\AddOns, but I don´t get the button.