Postmark(n.) The mark, or stamp, of a post office on a letter, giving the place and date of mailing or of arrival.
Postmark(v. t.) To mark with a post-office stamp; as, to postmark a letter or parcel.
Postmarked(imp. & p. p.) of Postmark
Postmarking(p. pr. & vb. n.) of Postmark

Words within postmark