Editing Procmail (section)

== Operation ==

procmail reads mail messages given to it on [[standard input]], delivering or otherwise dispositioning each one.  procmail is typically not invoked directly by the user.  Rather, some other mail program will call upon procmail to deliver a message according to the user's wishes.  [[Message transfer agent]]s (MTAs), such as [[Sendmail]] or [[Postfix (software)|Postfix]]), can be configured to use procmail to deliver all mail.  A [[mail retrieval agent]] such as [[fetchmail]] can invoke procmail as needed.  The companion tool ''formail'' allows procmail to be applied to mail already in a mailbox.

procmail's behavior is controlled by a [[configuration file|config file]] (by default, {{mono|.procmailrc}} in the user's [[home directory]]) containing one or more ''recipes'', read in order.  Each recipe consists of a ''mode'', zero or more ''conditions'', and an ''action''.

Conditions are usually extended [[regular expressions]], although there are other forms.  A recipe's action is taken only if all the conditions match (logical AND).  If no conditions is given, the recipe is unconditional and the action always runs.

The action specifies what is to be done with the message, such as deliver it to a particular mailbox, or discard it.  A recipe and its action can be ''delivering'' or ''non-delivering''.  Processing of a given message stops with the first delivering recipe (unless the recipe's mode flag specifies otherwise).