Hard-wrap message headers according to RFC

program/include/rcube_mail_mime.php

@@ -180,7 +180,7 @@ class rcube_mail_mime extends Mail_mime
         }
       }
 
-      $input[$hdr_name] = $hdr_value;
+      $input[$hdr_name] = wordwrap($hdr_value, 990, "\n", true);  // hard limit header length
     }
 
     return $input;

program/steps/mail/sendmail.inc

@@ -226,7 +226,7 @@ if (!empty($identity_arr['bcc']))
   $headers['Bcc'] = ($headers['Bcc'] ? $headers['Bcc'].', ' : '') . $identity_arr['bcc'];
 
 // add subject
-$headers['Subject'] = trim(get_input_value('_subject', RCUBE_INPUT_POST, FALSE, $message_charset));
+$headers['Subject'] = trim(get_input_value('_subject', RCUBE_INPUT_POST, TRUE, $message_charset));
 
 if (!empty($identity_arr['organization']))
   $headers['Organization'] = $identity_arr['organization'];