diff -ruN e-smith-email-5.0.0.old/root/usr/local/sbin/smtp-auth-proxy.pl e-smith-email-5.0.0/root/usr/local/sbin/smtp-auth-proxy.pl
--- e-smith-email-5.0.0.old/root/usr/local/sbin/smtp-auth-proxy.pl	2012-06-30 23:22:56.000000000 +0100
+++ e-smith-email-5.0.0/root/usr/local/sbin/smtp-auth-proxy.pl	2012-06-30 23:36:02.000000000 +0100
@@ -23,6 +23,7 @@
     my $smtp_proxy_rec = $config->get('smtp-auth-proxy');
 
     $prop->{SMTPSmartHost} = $config->get_value('SMTPSmartHost');
+    $prop->{Blacklist} = $smtp_proxy_rec->prop('Blacklist') || " ";
     $prop->{Userid} = $smtp_proxy_rec->prop('Userid');
     $prop->{Passwd} = $smtp_proxy_rec->prop('Passwd');
     $prop->{Debug} = $smtp_proxy_rec->prop('Debug');
@@ -92,7 +93,10 @@
 
     if ($smtp->supports("AUTH"))
     {
-        unless ($smtp->auth($name, $pass))
+	foreach (split (/ /, $self->get_property('Blacklist')))
+	  {${*$smtp}{'net_smtp_esmtp'}->{"AUTH"} =~ s/$_//;}
+	
+	unless ($smtp->auth($name, $pass))
         {
             print "451 Could not auth to mail server\n";
             warn "SMTP authentication with ISP server failed\n";