kubuntu users should do:
- open a terminal
- sudo cp kmail.antispamrc kmail.antispamrc.old
- sudo gedit kmail.antispamrc
- change [General]

tools= to the number of tools you have, included the popfile tool

in my situation it will be 12:
[General]
tools=12

add at the end of the file:

[Spamtool #12] <---- 12 if the spamtool ends at 11, like what i have
Ident=popfile
Version=1
VisibleName?=&POPFile
Executable=/bin/true
URL=http://popfile.sourceforge.net
PipeFilterName?=POPFile Check
PipeCmdDetect?=/bin/true
ExecCmdSpam?=/usr/share/popfile/reclassify.pl spam
ExecCmdHam?=/usr/share/popfile/reclassify.pl normal
DetectionHeader?=X-Text-Classification
DetectionPattern?=spam
UseRegExp?=0
SupportsBayes?=1

- save it
- sudo gedit /usr/share/popfile/reclassify.pl
- add the following lines:
#!/usr/bin/perl
use strict;
use XMLRPC::Lite;

# This XMLRPC client reclassifies a message
# REQUIRES X-POPFile-Link be enabled for all messages processed
# Usage:
# ./xmlrpc-reclassify.pl bucket < message

my $bucket;
die ( "You must specify a bucket!" ) unless ( $bucket = $ARGV[0] );

my $message;

# act like a pipe, reading from STDIN
while (<STDIN>) {
if ($_ =~ /^{X-POPFile-Link: .*?\?view=([0-9]+)/) {
$message = $1;
last;
}
}}

die ( "No X-POPFile-Link header found") unless ( defined( $message ) );

print STDERR "Reclassifying message $message to $bucket\n";

# our XMLRPC proxy
my $xmlrpc = XMLRPC::Lite ->proxy('http://localhost:8081/RPC2');

# say hello and get a session key
my $sk = $xmlrpc-> call('POPFile/API.get_session_key','admin',)
-> result;

die ( "Unable to obtain a session with POPFile. \
Please verify that POPFile is running and\

your username and password are correct. $sk" ) if ($sk eq !defined($sk) );