diff --git a/core/includes/mail.inc b/core/includes/mail.inc
index 5e89917..d1cc647 100644
--- a/core/includes/mail.inc
+++ b/core/includes/mail.inc
@@ -8,9 +8,14 @@
 /**
  * Auto-detect appropriate line endings for e-mails.
  *
- * $conf['mail_line_endings'] will override this setting.
+ * The default mail line ending is "\n", however this conditional will set the
+ * line ending to the Windows required "\r\n".
  */
-define('MAIL_LINE_ENDINGS', isset($_SERVER['WINDIR']) || strpos($_SERVER['SERVER_SOFTWARE'], 'Win32') !== FALSE ? "\r\n" : "\n");
+if (isset($_SERVER['WINDIR']) || strpos($_SERVER['SERVER_SOFTWARE'], 'Win32') !== FALSE) {
+  config('system.mail')
+    ->set('line_endings', '\r\n')
+    ->save();
+}
 
 /**
  * Composes and optionally sends an e-mail message.
@@ -214,12 +219,12 @@ function drupal_mail($module, $key, $to, $langcode, $params = array(), $from = N
  *
  * The selection of a particular implementation is controlled via the variable
  * 'system.mail.system', which is a keyed array.  The default implementation
- * is the class whose name is the value of 'default-system' key. A more specific
- * match first to key and then to module will be used in preference to the
- * default. To specificy a different class for all mail sent by one module, set
- * the class name as the value for the key corresponding to the module name. To
- * specificy a class for a particular message sent by one module, set the class
- * name as the value for the array key that is the message id, which is
+ * is the class whose name is the value of 'default' key. A more specific match
+ * first to key and then to module will be used in preference to the default. To
+ * specificy a different class for all mail sent by one module, set the class
+ * name as the value for the key corresponding to the module name. To specificy
+ * a class for a particular message sent by one module, set the class name as
+ * the value for the array key that is the message id, which is
  * "${module}_${key}".
  *
  * For example to debug all mail sent by the user module by logging it to a
@@ -227,7 +232,7 @@ function drupal_mail($module, $key, $to, $langcode, $params = array(), $from = N
  *
  * @code
  * array(
- *   'default-system' => 'Drupal\Core\Mail\PhpMail',
+ *   'default' => 'Drupal\Core\Mail\PhpMail',
  *   'user' => 'DevelMailLog',
  * );
  * @endcode
@@ -237,7 +242,7 @@ function drupal_mail($module, $key, $to, $langcode, $params = array(), $from = N
  *
  * @code
  * array(
- *   'default-system' => 'Drupal\Core\Mail\PhpMail',
+ *   'default' => 'Drupal\Core\Mail\PhpMail',
  *   'user' => 'DevelMailLog',
  *   'contact_page_autoreply' => 'DrupalDevNullMailSend',
  * );
@@ -273,7 +278,7 @@ function drupal_mail_system($module, $key) {
     $class = $configuration[$module];
   }
   else {
-    $class = $configuration['default-system'];
+    $class = $configuration['default'];
   }
 
   if (empty($instances[$class])) {
@@ -502,7 +507,7 @@ function drupal_html_to_text($string, $allowed_tags = NULL) {
         $chunk = $casing($chunk);
       }
       // Format it and apply the current indentation.
-      $output .= drupal_wrap_mail($chunk, implode('', $indent)) . MAIL_LINE_ENDINGS;
+      $output .= drupal_wrap_mail($chunk, implode('', $indent)) . config('system.mail')->get('line_endings');
       // Remove non-quotation markers from indentation.
       $indent = array_map('_drupal_html_to_text_clean', $indent);
     }
diff --git a/core/lib/Drupal/Core/Mail/PhpMail.php b/core/lib/Drupal/Core/Mail/PhpMail.php
index 8dac73d..fbbedda 100644
--- a/core/lib/Drupal/Core/Mail/PhpMail.php
+++ b/core/lib/Drupal/Core/Mail/PhpMail.php
@@ -59,7 +59,7 @@ public function mail(array $message) {
     foreach ($message['headers'] as $name => $value) {
       $mimeheaders[] = $name . ': ' . mime_header_encode($value);
     }
-    $line_endings = config('system.mail')->get('line_endings') ?: MAIL_LINE_ENDINGS;
+    $line_endings = config('system.mail')->get('line_endings');
     // Prepare mail commands.
     $mail_subject = mime_header_encode($message['subject']);
     // Note: e-mail uses CRLF for line-endings. PHP's API requires LF
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
index cfd1bf0..39e5af1 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
@@ -751,7 +751,7 @@ protected function setUp() {
     $this->resetAll();
 
     // Use the test mail class instead of the default mail handler class.
-    config('system.mail')->set('system', array('default-system' => 'Drupal\Core\Mail\VariableLog'))->save();
+    config('system.mail')->set('system', array('default' => 'Drupal\Core\Mail\VariableLog'))->save();
 
     drupal_set_time_limit($this->timeLimit);
     $this->setup = TRUE;
diff --git a/core/modules/system/config/system.mail.yml b/core/modules/system/config/system.mail.yml
index bdcced3..4672edc 100644
--- a/core/modules/system/config/system.mail.yml
+++ b/core/modules/system/config/system.mail.yml
@@ -1,2 +1,3 @@
 system:
-  'default-system': 'Drupal\Core\Mail\PhpMail'
+  'default': 'Drupal\Core\Mail\PhpMail'
+line_endings: '\n'
diff --git a/core/modules/system/lib/Drupal/system/Tests/Mail/HtmlToTextTest.php b/core/modules/system/lib/Drupal/system/Tests/Mail/HtmlToTextTest.php
index 06e230d..77d6d38 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Mail/HtmlToTextTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Mail/HtmlToTextTest.php
@@ -349,7 +349,7 @@ public function testVeryLongLineWrap() {
     $input = 'Drupal<br /><p>' . str_repeat('x', 2100) . '</><br />Drupal';
     $output = drupal_html_to_text($input);
     // This awkward construct comes from includes/mail.inc lines 8-13.
-    $eol = config('system.mail')->get('line_endings') ?: MAIL_LINE_ENDINGS;
+    $eol = config('system.mail')->get('line_endings');
     // We must use strlen() rather than drupal_strlen() in order to count
     // octets rather than characters.
     $line_length_limit = 1000 - drupal_strlen($eol);
diff --git a/core/modules/system/lib/Drupal/system/Tests/Mail/MailTest.php b/core/modules/system/lib/Drupal/system/Tests/Mail/MailTest.php
index 67423e1..a2229fa 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Mail/MailTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Mail/MailTest.php
@@ -42,7 +42,7 @@ function setUp() {
     parent::setUp();
 
     // Set MailTestCase (i.e. this class) as the SMTP library
-    config('system.mail')->set('system', array('default-system' => 'Drupal\system\Tests\Mail\MailTest'))->save();
+    config('system.mail')->set('system', array('default' => 'Drupal\system\Tests\Mail\MailTest'))->save();
   }
 
   /**