Drop mail_header_delimiter option, since we don't use mail() we don't need it

config/defaults.inc.php

@@ -538,10 +538,6 @@ $config['http_received_header'] = false;
 // when tracking down issues.
 $config['http_received_header_encrypt'] = false;
 
-// This string is used as a delimiter for message headers when sending
-// a message via mail() function. Leave empty for auto-detection
-$config['mail_header_delimiter'] = NULL;
-
 // number of chars allowed for line when wrapping text.
 // text wrapping is done when composing/sending messages
 $config['line_length'] = 72;

program/include/rcmail_install.php

@@ -750,10 +750,6 @@ class rcmail_install
                 return $val;
             }
             break;
-
-        case 'mail_header_delimiter':
-            $var = str_replace(array("\r", "\n"), array('\r', '\n'), $var);
-            return '"' . $var. '"';
 /*
         // RCMAIL_VERSION is undefined here
         case 'useragent':

program/lib/Roundcube/rcube_config.php

@@ -535,6 +535,7 @@ class rcube_config
      * Try to autodetect operating system and find the correct line endings
      *
      * @return string The appropriate mail header delimiter
+     * @deprecated Since 1.3 we don't use mail()
      */
     public function header_delimiter()
     {