NAME
    Net::SMTP::Receive - receive mail via SMTP

SYNOPSIS
            MyMailReceiver->showqueue()

            MyMailReceiver->runqueue()

            MyMailReceiver->server(%options)

            package MyMailReceiver;

            @ISA = qw(Net::SMTP::Receive);

            use Net::SMTP::Receive;

            sub deliver
            {
                    my ($message) = @_;

                    # attempt to deliver a message...
                    die or return, return code ignored
            }

            sub is_delivered
            {
                    my ($message, $recipient) = @_;

                    if ($recipient) {
                            return 1 if delivered to recipient
                            return 0 if not
                    } 
                    return 1 if message is fully delivered
                    return 0 if not
            }

DESCRIPTION
    Net::SMTP::Receive handles receiving email via SMTP. It is built as a
    base class that must be subclassed to provide methods for actually
    delivering a message. Many aspects of Net::SMTP::Receive's behavior can
    be modified by overriding methods in the subclass.

    Net::SMTP::Receive does not provide any method to deliver a message or
    even check that it has been delivered. That's left for the subsclass.
    However, it will queue the message until it has been delivered.

    Almost all configuration of Net::SMTP::Receive is done through
    overriding method definitions.

    Both the SMTP server and individual messages are represented by
    Net::SMTP::Receive objects (or rather MyMailReceiver objects if that's
    what you choose to name your subclass).

    This module defines the pieces you need for a basic mail server but it
    since some of the bits must be overriden, it does not define a complete
    mail server. A complete mail server, listens for connections, queues
    mail, re-runs the queue every now and then, and can display the queue. A
    call to "serer()" will listen for conenctions. It blocks forever. A call
    to "runqueue()" will process the pending queue. Arrange to call this
    periodically. A call to "showqueue()" will display the queue: provide a
    command to for users to do this. This is not meant as a high-volume mail
    server. It is mean to provide a way to directly receive mail in perl
    while honoring the guarantees that mail servers should make.

MEMBER DATA
    The following fields exist the sever objects and continue to exist as
    the server object forks itself to become a message object.

    PEERHOST, PEERADDR
        "PEERADDR" is the IP address of the system the email is coming from.
        "PEERHOST" is the hostname of the system the email is coming from.

    IDENT
        "IDENT" is the username returned by doing an ident query on the
        sender.

    HELO
        "HELO" is a copy of the greeting sent by the client.

    MIMETYPE
        "MIMETYPE" is either "8BITMIME" or "7BIT" depending on the transfer
        encoding used.

    FROM
        "FROM" is the address provided with "MAIL FROM".

    TO  "TO" is an anonymous array of addresses provided by the "RCPT TO"
        command. This array may be modified by the "deliver()" method.

    TIME
        "TIME" is a timestamp (integer) of when the message was first
        enqueued.

    ID  "ID" is the identification assigned to the message as it is
        enqueued. The filename of the message is
        "$queue_directory/$message-"{ID}.txt> (also available as
        "$message-"{TEXTFILE}>). The envelope is stored as a perl object in
        "$queue_directory/$message-"{ID}.pqf>.

    TEXTFILE
        "TEXTFILE" is the filename where the message is stored while in the
        message queue. Messages are placed in the queue before delivery is
        attempted.

    ERROR
        "ERROR" contains the die message ($@) from the last delivery
        attempt.

    LASTRUN
        "LASTRUN" is the timestamp (integer) of when delivery was last
        attempted on the message.

    STATE
        "STATE" is a status field that is left over from the protocol
        negotiations. It's mentioned here because it's reserved for internal
        use. Any additional fields added after this release will use a
        member data naming prefix of "NSR_".

REQUIRED METHODS TO OVERRIDE
    You must override "deliver" and "is_delivered". In the context of method
    delivery, $message is a persistent object. You can add or change fields
    and unless the message is fully delivered, your changes stored with
    Storable and restored the next time delivery() is attempted.

    See the "MEMBER DATA" section for the pre-defined keys that the message
    object provides.

    For "is_delivered" the recipient optional. If present, the return value
    is used for for "showqueue".

    For "deliver", it is okay to "die". If you do, the die message will
    become the "ERROR" field and be displayed by "showqueue". Delivery will
    be re-attempted by "runqueue".

ADDITIONAL METHODS TO OVERRIDE
    The following is not a complete set, but it is likely to be enough. For
    the complete set, read the source.

    "check_rcptto()" is an important method to define. It is here that it is
    easiest to prevent open relaying. A simple check that the recipient
    address belongs to you will do. A return code of something like: "550
    relaying denied" works.

            sub check_rcptto
            {
                    my ($self, $envelope_to_address) = @_;

                    return 0 if the address is okay as it stands
                    return (0, @replacement_addresses) if the address is okay
                            but delivery should be redirected to antoher 
                            address or addresses.
                    return "550 relaying denied, so go away!"
            }

    "check_mailfrom" is less important, but can also be useful.

            sub check_mailfrom
            {
                    my ($self, $envelope_from_address) = @_;

                    return 0 if the from address is okay
                    return $smtp_3digit_error_code otherwise
            }

            sub do_syslog
            {
                    return 1 if you want syslogging of activity
                    return 0 if you want errors to stderr
            }

            sub queue_directory 
            {
                    return '/var/spool/pmqueue';
                    # return something else to place the message queue
                    # elsewhere.
            }

            sub checkaccess
            {
                    my ($self, $client_iohandle, $remote_ident) = @_;

                    die or exit() if you don't want to talk to the client
                    otherwise, return anything
            }

            sub prestart
            {
                    my ($self, %config) = @_;

                    # initialize any special MyMailReceiver state before
                    # starting to listen as a server
            }

            sub max_datalength
            {
                    return 20_000_000; 
                    # return something smaller if you don't want to accept
                    # 20GB messages..
            }

            sub max_recipients
            {
                    return 10_000;
                    # return something smaller if you want to place a more
                    # reasonable limit on the number of recipients.
            }

            sub add_envelope
            {
                    return 0; #default
                    return 1 
                    # if you want to add an C<X-Envelope-To:> header.
                    # If you do this, C<Bcc:> won't be blind.
            }

            sub predeliver
            {
                    my ($msg, $client, $msgref) = @_;
                    # check over the incoming message before it is enqueued
                    # this is a good place to enforce policy or do quick
                    # spam checks.  Die with an SMTP error code to reject
                    # the message --- die "500 relaying denied"
                    # The $msgref is an anonymous list comprising the body
                    # of the message.
                    die "500 relaying denied" if $msgref->[0] !~ /\@myhost/;
                    return 0
            }

METHODS TO CALL
    Net::SMTP::Receive has three core methods that are used to fire it up.

            MyMailReceiver->server(%config)

    "server()" starts an SMTP listening server. The config parameters
    currently supported are:

            IPAddr
            Port

            MyMailReceiver->runqueue()

    "runqueue()" processes the mail queue. It is not called automatically by
    the server. Call it with a cron job instead. Be sure to do this!

            MyMailReceiver->showqueue([$message ids])

    "showqueue()" prints a sendmail-style mail queue report to STDOUT. It is
    optionally restricted to particular message ids.

    Net::SMTP::Receive doesn't provide much for the subclass to call.
    However, there are a few methods that might be some help. Well, one
    anyway:

            $message->log($text, $args)

    syslog()s text and also printf's it.

LICENSE
    Copyright (C) 2001, 2002 David Muir Sharnoff. License hereby granted for
    anyone to use, modify or redistribute this module at their own risk.
    Please feed useful changes back to muir@idiom.org.

