diff --git a/Debbugs/User.pm b/Debbugs/User.pm
index 9f64be3f..86e60b19 100644
--- a/Debbugs/User.pm
+++ b/Debbugs/User.pm
@@ -105,10 +105,36 @@ BEGIN {
 #######################################################################
 # Helper functions

+our $_lists;
+sub is_valid_package {
+  my $p = shift;
+
+  unless ($_lists) {
+    my $file = "$config{config_dir}/Lists";
+    my %lists;
+    my $pkg;
+
+    open(FILE,"<$file" ) || die "$file open: $!";
+
+    while(<FILE>) {
+
+      next unless m/^(\S+)\s+(\S.*\S)\s*$/;
+      $pkg = $1;
+      $pkg =~ y/A-Z/a-z/;
+      $lists{$pkg}++;
+    }
+
+    close(FILE);
+
+    $_lists = \%lists;
+  }
+
+  return ${$_lists}{$p};
+}
+
 sub is_valid_user {
     my $u = shift;
-    return ($u =~ /^[a-zA-Z0-9._+-]+[@]?[a-zA-Z0-9-.]{4,}$/);
-#    return ($u =~ /^[a-zA-Z0-9._+-]+[@][a-z0-9-.]{4,}$/);
+    return ($u =~ /^[a-zA-Z0-9._+-]+[@][a-z0-9-.]{4,}$/) || (is_valid_package($u));
 }

 #######################################################################