diff --git a/config.sample/relayclients b/config.sample/relayclients
index 792c76b..a0fbc4e 100644
--- a/config.sample/relayclients
+++ b/config.sample/relayclients
@@ -4,3 +4,9 @@
 127.0.0.1 
 # leading/trailing whitespace is ignored
  192.0. 
+#
+# IPv6 formats ends in a nibble (not a netmask, prefixlen, or colon)
+# RFC 3849 example
+2001:DB8
+2001:DB8::1
+2001:0DB8:0000:0000:0000:0000:0000:0001
diff --git a/plugins/sender_permitted_from b/plugins/sender_permitted_from
index d888701..42f26d8 100644
--- a/plugins/sender_permitted_from
+++ b/plugins/sender_permitted_from
@@ -59,6 +59,8 @@ use warnings;
 #use Mail::SPF 2.000;   # eval'ed in ->register
 use Qpsmtpd::Constants;
 
+use Net::IP;
+
 sub register {
     my ($self, $qp, %args) = @_;
     eval 'use Mail::SPF';
@@ -237,13 +239,27 @@ sub is_in_relayclients {
     my $more_relay_clients = $self->qp->config('morerelayclients', 'map');
     my %relay_clients      = map { $_ => 1 } @relay_clients;
 
+    my $ipv6 = $client_ip =~ /:/ ? 1 : 0;
+
+    if ( $ipv6 && $client_ip =~ /::/ ) {  # IPv6 compressed notation
+        $client_ip = Net::IP::ip_expand_address($client_ip,6);
+    };
+
     while ($client_ip) {
         if ( exists $relay_clients{$client_ip} ||
              exists $more_relay_clients->{$client_ip} ) {
             $self->log( LOGDEBUG, "skip, IP in relayclients" );
             return 1;
         };
-        $client_ip =~ s/\d+\.?$// or last;   # strip off another 8 bits
+
+        # added IPv6 support (Michael Holzt - 2012-11-14)
+        if ( $ipv6 ) {
+            $client_ip =~ s/[0-9a-f]:*$//;       # strip off another nibble
+            chop $client_ip if ':' eq substr($client_ip, -1, 1);
+        }
+        else {
+            $client_ip =~ s/\d+\.?$// or last;   # strip off another 8 bits
+        }
     }
     return;
 };