GNU/Linux Desktop Survival Guide
by Graham Williams
Procmail: Filter and Split Incoming Email
The procmail package provides a powerful mechanism for filtering incoming email, to split email that meet certain criteria into separate folders, to forward different emails on to other users, and to add extra headers to your email (e.g., X-Label headers to classify your email into categories you might define).
The procmail application will be invoked on any email
that arrives for you by adding the following to your .forward
At the heart of procmail is the .procmailrc file. This contains all the rules that are applied to an email to determine what should happen to that email.
There is potential for procmail to be invoked in rapid succession, and thus if two procmails try to write to the one file there could be a problem. Thus procmail uses lock files to ensure this does not happen. A lock file will slow procmail down ever so slightly, so it is kept as an option specified in the configuration file (.procmailrc) rather than a default.