Bug 405453: Make Bugzilla encode all outgoing email headers.

Bugzilla/Mailer.pm

@@ -96,8 +96,11 @@ sub MessageToMTA {
     $email->header_set('MIME-Version', '1.0') if !$email->header('MIME-Version');
 
     # Encode the headers correctly in quoted-printable
-    foreach my $header qw(From To Cc Reply-To Sender Errors-To Subject) {
-        if (my $value = $email->header($header)) {
+    foreach my $header ($email->header_names) {
+        my @values = $email->header($header);
+        # We don't recode headers that happen multiple times.
+        next if scalar(@values) > 1;
+        if (my $value = $values[0]) {
             if (Bugzilla->params->{'utf8'} && !utf8::is_utf8($value)) {
                 utf8::decode($value);
             }