Index: includes/mail.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/mail.inc,v
retrieving revision 1.9
diff -u -p -r1.9 mail.inc
--- includes/mail.inc	6 Feb 2008 19:38:26 -0000	1.9
+++ includes/mail.inc	14 Mar 2008 23:20:48 -0000
@@ -184,10 +184,12 @@ function drupal_mail_send($message) {
     return mail(
       $message['to'],
       mime_header_encode($message['subject']),
-      // Note: e-mail uses CRLF for line-endings, but PHP's API requires LF.
+      // Note: e-mail uses CRLF for line-endings, but PHP's API requires LF
+      // for the message body.
       // They will appear correctly in the actual e-mail that is sent.
       str_replace("\r", '', $message['body']),
-      join("\n", $mimeheaders)
+      // For headers, PHP's API requires that we use CRLF normally.
+      join("\r\n", $mimeheaders)
     );
   }
 }