All is OK except for a problem in the installation of Courier::Filter
my /var/log/maillog file it appears the message:
"courierfilter: Unable to create socket
/usr/share/courier-filter-perl/perl5/Courier/Filter.pm line 307."
That means that the /var/lib/courier/allfilters/ directory either doesn't
exist or isn't writable for the "daemon" (or "courier") system user.
You probably forgot to adjust the paths in the Courier/Config.pm file to
the paths used by your system. The "Courier::Filter::Overview" documenta-
tion explains how to install Courier::Filter. Have you read it?
I reviewed the line of Filter.pm and I suppose that it must to
a problem of IO::Socket::UNIX module,
and I have seen in www.cpan.org that IO:Socket:UNIX comes with
Perl 5.8.6 it wanted to know if this is correct.
IO::Socket::UNIX has been included with the standard Perl distribution for
a long time. That should not be your problem.