The MAIL.DELIVERY file controls DELIVER and tells it how to
    handle each incoming message. A MAIL.DELIVERY file consists of
    a series of directives with one directive on each line of the
    file. Each directive specifies how a certain kind of message is
    to be handled. A particular directive may or may not apply to a
    given message. An attempt is made to apply every directive in the
    MAIL.DELIVERY file to each message, thus more than one directive
    may apply to (and more than one action may be the result of) a
    single message.

    Any line in the file which begins with a semicolon or an
    exclamation point is considered to be a comment and is ignored.

    A directive line consists of the following items in order from
    left to right:

 1-pattern 2-pattern 3-pattern accept action 1-parameter 2-parameter

    Items must be delimited by one or more spaces or tabs. Quoted
    strings (use double quotes, not single quotes) are allowed as
    single items; the quotes are removed from the items as they
    are read. A double quote can be obtained by using two double
    quotes with no space between them. This form of quote handling is
    consistent with that of OpenVMS DCL.

    The 1-PARAMETER and 2-PARAMETER items are both optional and can
    be omitted if the action ACTION requires no parameters. The first
    five items are mandatory and must appear in every directive line.