Mailing is the act of sending letters, packages, or other items through the postal system. When you write a letter to your grandmother and drop it in a blue mailbox, you're mailing it to her. When a company sends you a birthday catalog, that's a mailing they've sent to customers.

Before email and text messages existed, mailing letters was the main way people communicated across distances. People would eagerly check their mailboxes for letters from friends and family. Even today, mailing remains important for sending packages, legal documents, greeting cards, and items that need a physical signature.

The word can also refer to a large batch of items sent at once. A school might do a mailing to all parents about an upcoming event, sending the same letter to hundreds of families. Political campaigns often send mass mailings with information about candidates.

Related words include mail (the letters and packages themselves), mailbox (where mail is delivered or collected), and mailer (either a person who sends mail or a special envelope designed for mailing). The worker who delivers your mail is sometimes called a letter carrier or mail carrier.