1. postmark - Noun
2. postmark - Verb
The mark, or stamp, of a post office on a letter, giving the place and date of mailing or of arrival.
To mark with a post-office stamp; as, to postmark a letter or parcel.
Source: Webster's dictionaryA first day cover usually consists of an envelope, a postage stamp and a postmark with the date of the stamp’s first day of issue thereon. Source: Internet
A postage meter imprints an amount of postage, functioning as a postage stamp, a cancellation and a dated postmark all in one. Source: Internet
Appel and Haken's announcement was widely reported by the news media around the world, and the math department at the University of Illinois used a postmark stating "Four colors suffice." Source: Internet
At this ceremony, attendees could attach the Duke stamp to an envelope and get it canceled with a First Day of Issue postmark. Source: Internet
Asked about the number of mail ballots that missed the Nov. 3 postmark cutoff, the U.S. Postal Service referred back to local election officials for comment. Source: Internet
After applying the first day of issue postmark, the Postal Service will return the envelopes through the mail. Source: Internet