--- amavisd.orig        2008-06-29 08:37:58.000000000 +0800
+++ amavisd     2008-08-21 19:28:52.000000000 +0800
@@ -2026,6 +2026,7 @@
 use subs @EXPORT_OK;
 
 use Errno qw(ENOENT EACCES EAGAIN ESRCH);
+use POSIX qw(isprint);
 use IO::File ();
 use Digest::MD5 2.22;  # need 'clone' method
 # use Encode;  # Perl 5.8  UTF-8 support
@@ -2077,13 +2078,74 @@
   }
 }
 
-sub safe_decode($$;$) {
-  if (!$unicode_aware) { $_[1] }  # just return the second argument
-  else {
+sub isbig5($)
+{
+  my $code = shift;
+
+  if (length($code) >= 2)
+  {
+    my @code = split '', $code;
+    if (ord($code[0]) < 161)
+    {
+      return (0);
+    }
+    else
+    {
+      if (((ord($code[1]) >= 64) && (ord($code[1]) <= 126)) ||
+          ((ord($code[1]) >= 161) && (ord($code[1]) <= 254)))
+      {
+        return (1);
+      }
+    }
+  }
+  return (0);
+}
+
+sub isbig5str($)
+{
+  my $astr = shift;
+  my $alen = length($astr);
+  my $rlen = 0;
+
+  while ($rlen < $alen)
+  {
+    if (isbig5(substr($astr, $rlen, $alen - $rlen)))
+    {
+      $rlen += 2;
+    }
+    elsif (isprint(substr($astr, $rlen, 1)))
+    {
+      $rlen += 1;
+    }
+    else
+    {
+      return (0);
+    }
+  }
+  return (1);
+}
+
+sub safe_decode($$;$)
+{
+  if (!$unicode_aware)
+  {
+    $_[1];
+  } # just return the second argument
+  else
+  {
     my($encoding,$str,$check) = @_;
-    $check = 0  if !defined($check);
-    my($taint) = substr($str,0,0);  # taintedness of the string
-    $taint . Encode::decode($encoding,untaint($str),$check);  # preserve taint
+    $check = 0 if !defined($check);
+    my($taint) = substr($str,0,0); # taintedness of the string
+    my($u_str) = untaint($str);
+    my($d_str) = $taint . Encode::decode($encoding,$u_str,$check); # preserve
+    if (($d_str eq $u_str) && isbig5str($u_str))
+    {
+      $taint . Encode::decode("big5",$u_str,$check)
+    }
+    else
+    {
+      $d_str;
+    }
   }
 }
 
@@ -12554,7 +12616,7 @@
   Amavis::Lookup::RE->new(@$Amavis::Conf::map_full_type_to_short_type_re);
 
 # default location of the config file if none specified
-push(@config_files, '/etc/amavisd.conf')  if !@config_files;
+push(@config_files, '/usr/local/etc/amavisd.conf')  if !@config_files;
 # Read and evaluate config files, which may override default settings
 Amavis::Conf::include_config_files(@config_files);
 Amavis::Conf::supply_after_defaults();