3.2 Simplest Configurations

The mailfromd script file contains a series of declarations of the handler procedures. Each declaration has the form:

prog name
do
  …
done

where prog, do and done are the keywords, and name is the state name for this handler. The dots in the above example represent the actual code, or a set of commands, instructing mailfromd how to process the message.

For example, the declaration:

prog envfrom
do
  accept
done

installs a handler for ‘envfrom’ state, which always approves the message for delivery, without any further interaction with mailfromd.

The word accept in the above example is an action. Action is a special language statement that instructs the run-time engine to stop execution of the program and to return a response code to the Sendmail. There are five actions, one for each response code: continue, accept, reject, discard, and tempfail. Among these, reject and discard can optionally take one to three arguments. There are two ways of supplying the arguments.

In the first form, called literal or traditional notation, the arguments are supplied as additional words after the action name, separated by whitespace. The first argument is a three-digit RFC 2821 reply code. It must begin with ‘5’ for reject and with ‘4’ for tempfail. If two arguments are supplied, the second argument must be either an extended reply code (RFC 1893/2034) or a textual string to be returned along with the SMTP reply. Finally, if all three arguments are supplied, then the second one must be an extended reply code and the third one must supply the textual string. The following examples illustrate all possible ways of using the reject statement in literal notation:

reject
reject 503
reject 503 5.0.0
reject 503 "Need HELO command"
reject 503 5.0.0 "Need HELO command"

Please note the quotes around the textual string.

Another form for these action is called functional notation, because it resembles the function syntax. When used in this form, the action word is followed by a parenthesized group of exactly three arguments, separated by commas. The meaning and ordering of the argument is the same as in literal form. Any of three arguments may be absent, in which case it will be replaced by the default value. To illustrate this, here are the statements from the previous example, written in functional notation:

reject(,,)
reject(503,,)
reject(503, 5.0.0)
reject(503,, "Need HELO command")
reject(503, 5.0.0, "Need HELO command")