#239825 by jeffschuler and bjaspan: Add support for OS-specific line endings on e-mails.

includes/mail.inc

@@ -6,6 +6,12 @@
  * API functions for processing and sending e-mail.
  */
 
+/**
+ * Auto-detect appropriate line endings for e-mails.
+ * $conf['mail_line_endings'] will override this setting.
+ */
+define('MAIL_LINE_ENDINGS', isset($_SERVER['WINDIR']) || strpos($_SERVER['SERVER_SOFTWARE'], 'Win32') !== FALSE ? "\r\n" : "\n");
+
 /**
  * Compose and optionally send an e-mail message.
  *

modules/system/mail.sending.inc

@@ -45,12 +45,13 @@ public function mail(array $message) {
     foreach ($message['headers'] as $name => $value) {
       $mimeheaders[] = $name . ': ' . mime_header_encode($value);
     }
+    $line_endings = variable_get('mail_line_endings', MAIL_LINE_ENDINGS);
     return mail(
       $message['to'],
       mime_header_encode($message['subject']),
-      // Note: e-mail uses CRLF for line-endings, but PHP's API requires LF.
-      // They will appear correctly in the actual e-mail that is sent.
-      str_replace("\r", '', $message['body']),
+      // Note: e-mail uses CRLF for line-endings. PHP's API requires LF
+      // on Unix and CRLF on Windows. See mail_line_endings in settings.php.
+      preg_replace('@\r?\n@', $line_endings, $message['body']),
       // For headers, PHP's API suggests that we use CRLF normally,
       // but some MTAs incorrectly replace LF with CRLF. See #234403.
       join("\n", $mimeheaders)

sites/default/default.settings.php

@@ -166,6 +166,15 @@
  */
 $update_free_access = FALSE;
 
+/**
+ * Line endings for e-mail messages
+ * 
+ * Drupal automatically guesses the line-ending format appropriate for your 
+ * system. If you need to override this, uncomment the statement below and set
+ * it to the line-ending string of your choice.
+ */
+# $conf['mail_line_endings'] = "\r\n";
+
 /**
  * Base URL (optional).
  *