Can the post office be postmarked free of charge?

Although the post office can be postmarked free of charge, it is not casually stamped. Generally, on certain days, such as festivals, postmarks can be stamped free of charge.

Postmark is a kind of postmark stamped by the post office on the actually sent mail package, including ordinary postmark, commemorative postmark, publicity postmark and so on. Is a reflection of history. Collecting postmarks has become an important part of stamp collecting.