a piece of ((computer science) written programs or procedures or rules and associated documentation pertaining to the

a program that automatically processes messages sent to you before they are delivered to your inbox

a program that sits between your local delivery agent and you, automatically dispatching or rejecting mail before you see it

A program allowing email sorting before viewing by filtering the subject, sender's email address or information in the body of the message.

a program allowing the user to sort email according to its subject or heading.

A program that allows you to sort email before viewing it using the subject, the sender's email address, or even information in the body of the message. Eudora and Pegasus both have mail filtering options.

A program that allows the user to sort email messages according to information contained in the header.

A program which sorts and processes incoming mail based on patterns found in the mail headers. Source: Foldoc: Free On-line Dictionary of Computing

A program that allows you to sort e-mail according to information in the header.

A program which can sort and process incoming email for the recipient, based on the mail headers or content. For example, all mail pertaining to a certain subject (as indicated by its header) could be put into a high-priority file.