1. the act or process of stamping mail with an official mark showing the date and place of mailing

1. present participle of postmark; stamping mail with an official mark showing the date and place of mailing

Examples

• The postmarking of letters happens automatically at the sorting facility.
• She was responsible for postmarking all outgoing mail before 5 PM.
• The postmarking process helps track when and where mail was sent.
• Due to equipment failure, the postmarking was delayed by several hours.
• The postal worker was postmarking hundreds of envelopes.
• Clear postmarking ensures proper delivery tracking.