procmailrc

Procmail is a mail filtering and delivery agent for mail servers, allowing users to customize the filtering and handling of their email. The procmailrc file is a configuration file that contains a set of commands and rules that determine how procmail processes and delivers incoming email.

A procmailrc file typically contains a series of conditions and actions that are executed in response to a message. Conditions can be based on various criteria such as the recipient's email address, the sender's email address, the subject of the message, or the contents of the message itself. These conditions are then used to direct the message to a specific folder, pipe it through a program, or delete it.

The procmailrc file also allows users to define various functions and variables that can be used throughout the file. These can include directives for executing commands, setting environment variables, and storing values in variables. Procmail also provides a number of built-in variables that can be used in the file, such as $1, $2, and $3, which represent the first, second, and third command-line arguments respectively.

Procmail supports multiple delivery agents, allowing users to specify different delivery agents for different conditions. This allows for complex routing and filtering of email, making it a popular choice for users who require advanced mail filtering and delivery capabilities.

Procmail is available for a wide range of operating systems, including many Unix variants, Linux distributions, and some versions of Windows. It is commonly used on systems that run the Sendmail or Postfix mail servers, although it can also be used with other mail servers.