Antonyms for the word "postmarks" include different words related to the opposite meaning of this term, such as "prestige," "dignity," "honor," and "respectability." These antonyms refer to qualities that define a person or an action as reputable, respectable, and of high social status. Another antonym for "postmarks" could be "undistinguished," "ignoble," or "notable," emphasizing the lack of recognition or value to some actions or individuals. Alternatively, "beforedate" could also be considered an antonym, meaning an action or event that precedes a specific date, contrary to the significance of the postmark, which implies the date the mail was delivered.