Eeerm... Yeah, could be that somehow it has no content data. I made another MIME::Lite-Object, where I put my attachments. Then I attached this one to my $msg. Donīt ask me why, but it works! Looks like this:

$part_content = MIME::Lite->new(
            Type => 'text/plain',
            Data => $text_mail,
            Encoding => 'quoted-printable',
        );

        $part_content->attach(
            Type => 'application/pdf',
            Data => $pdf,   
            Filename => q(buchung_).$token.q(.pdf),
            Disposition => 'attachment'                
        );
# and then:
$msg->attach($part_content);
$msg->send || print "you DON'T have mail!";
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