Just to add some code that can be used as is, I have written a subclass for Apache::AntiSpam by Tatsuhiko Miyagawa, that implements this method. The code is not perfect but working. I also sended this to Tatsuhiko and asked him to bundle this with his modules.

package Apache::AntiSpam::SpamTrap;

use strict;
use vars qw($VERSION);
$VERSION = '0.01';

use Apache::AntiSpam;
use Apache::Constants qw(:common);
use base qw(Apache::AntiSpam);
use Crypt::Blowfish;

sub antispamize {
    my($class, $email, $orig) = @_;
    # this seems not very efficient
    my $r = Apache->request();
    # better error handling?
    my $key = $r->dir_config('Key') || return SERVER_ERROR;
    my $ip = $r->get_remote_host || return SERVER_ERROR;
    my $time = time;
    my $string = spamtrap_encode($ip, $time, $key);
    $orig =~ s/\@/-$string\@/;
    return $orig;
}    

sub spamtrap_encode
  {
    my ($ip, $time, $key) = @_;
    return unless $key;
    return unless $time > 0;
    return unless $ip =~ /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/o;
    my $inkey = pack("H16", $key);
    my $plaintext = join("", map { chr } split (/\./, $ip)) . pack("L"
+, $time);
    my $cipher = new Crypt::Blowfish $inkey;
    my $string = unpack("H*", $cipher->encrypt($plaintext));
    return $string;
  }


1;
__END__

=head1 NAME

Apache::AntiSpam::SpamTrap - Add SpamTrap suffix to local-part in Emai
+l

=head1 SYNOPSIS

  # in httpd.conf
  <Location /antispam>
  SetHandler perl-script
  PerlAddVar Key 0123456789ABCDEF
  PerlHandler Apache::AntiSpam::SpamTrap
  </Location>

  # filter aware
  PerlModule Apache::Filter
  SetHandler perl-script
  PerlSetVar Filter On
  PerlHandler Apache::RegistryFilter Apache::AntiSpam::SpamTrap Apache
+::Compress

=head1 DESCRIPTION

Apache::AntiSpam::SpamTrap is a subclass of Apache::AntiSpam, filter
module to prevent e-mail addresses exposed as is on web pages. This
module adds a Blowfish encrypted string suffix to the local-part of 
e-mail addresses. This string contains a timestamp and the IP address
of the remote host. This enables you to identify a spammer's address
harvester by its IP address and take steps to prosecute him.

The encryption prevents faking and may help in a prosecuting attemp.

For example, C<apleiner@cpan.org> will be filtered to
C<apleiner-78c1ed6da0322b3a@cpan.org>.

This module is Filter aware, meaning that it can work within
Apache::Filter framework without modification.

You need to give the Blowfish key in your Apache configuration file.

To decode a received mail's SpamTrap string use the following function
+:

  sub spamtrap_decode
    {
      my ($string, $key) = @_;
      return unless $key;
      return unless $string =~ /[0-9a-f]{16}/o;
      my $inkey = pack("H16", $key);
      use Crypt::Blowfish;
      my $cipher = new Crypt::Blowfish $inkey;
      my $plaintext = $cipher->decrypt(pack("H*", $string));
      my $time = unpack("L", substr($plaintext, 4, 4));
      my $ip = join(".", map { ord } split //, substr($plaintext, 0, 4
+));
      return wantarray ? ($ip, $time) : "$ip $time";
    }


=head1 TODO

=over 4

=item *

should make local address part be configured.

=back

=head1 AUTHOR

Alex Pleiner <alex@zeitform.de> - zeitform Internet Dienste 2003

This work is based on the Apache::AntiSpam::* modules provided by
Tatsuhiko Miyagawa <miyagawa@bulknews.net>. The idea is taken from
Daniel A. Rehbein (http://daniel.rehbein.net/).

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

=head1 SEE ALSO

L<Apache::AntiSpam>

=cut
[download]

alex pleiner <alex@zeitform.de>
zeitform Internet Dienste

++ to you. I enjoyed this idea very, very much. I've never heard of this before, but it seems brilliant. /me stops gushing.

Superaffenturbotittengeil!

--
Allolex

I am going to spread the voice at SourceForge to come and read this article- This would work great at that site!

Because they manage all the developers' email addresses. Actually, I think that there is a way of including all the non-*NIX users as well to enjoy this great tool. (I mean that not everybody has lots of composed email addresses just a single one. )

But I heard something of putting 2 @domain.com endings at an email address. It was done for re-routing emails through a different path in the Internet net.

Isn't it possible to apply that piece of password in some similar way so that it is not going to be interpreted by any email server and could reach to every email address?

I would give you the NOBEL Price, if I could vote for it!

corrected title (in English) for future searchers:
Re: Anti-Spam Mail Address Encoding (with encrypted IP Address)

You wrote:

21: # The method proposed by this encoder creates mail addresses
22: # that include a timestamp and the ip address of the remote
23: # host (i.e. of the harvester). This enables you to reveal
24: # the harvester's ip adress for received spam.