#!/usr/bin/perl
use warnings;
use strict;

use IO::Socket::INET;
use Net::Server::Mail::SMTP;

#our $host = $ARGV[0] || "157.163.168.131" ;
$| = 1;
 
my @local_domains = qw(example.com example.org);
my $server = IO::Socket::INET->new(Listen => 1, LocalPort => 25);
 
print "Waiting for incoming SMTP connections\n";
my $conn;
while($conn = $server->accept)
{
    my $smtp = Net::Server::Mail::SMTP->new(socket => $conn);
    $smtp->set_callback(RCPT => \&validate_recipient);
    $smtp->set_callback(DATA => \&queue_message);
    $smtp->process() or die $!;
    $conn->close();
}
 
sub validate_recipient
{
    my($session, $recipient) = @_;
 
    my $domain;
    if($recipient =~ /@(.*)>\s*$/)
    {
        $domain = $1;
    }
 
    if(not defined $domain)
    {
        return(0, 513, 'Syntax error.');
    }
    elsif(not(grep $domain eq $_, @local_domains))
    {
        return(0, 554, "$recipient: Recipient address rejected: Relay access denied");
    }
 
    return(1);
}
 
sub queue_message
{
    my($session, $data) = @_;
 
    my $sender = $session->get_sender();
    my @recipients = $session->get_recipients();
 
    return(0, 554, 'Error: no valid recipients')
        unless(@recipients);
 
    my $msgid = add_queue($sender, \@recipients, $data)
      or return(0);
 
    return(1, 250, "message queued $msgid");
}