Index: mail.inc
===================================================================
--- mail.inc	(revision 125)
+++ mail.inc	(working copy)
@@ -279,7 +279,7 @@
   // 'See <a href="http://drupal.org">the Drupal site</a>' becomes
   // 'See the Drupal site [1]' with the URL included as a footnote.
   _drupal_html_to_mail_urls(NULL, TRUE);
-  $pattern = '@(<a[^>]+?href="([^"]*)"[^>]*?>(.+?)</a>)@i';
+  $pattern = '@(<a[^>]+?href="([^"]*)"[^>]*?>(.+?)</a>)@is';
   $string = preg_replace_callback($pattern, '_drupal_html_to_mail_urls', $string);
   $urls = _drupal_html_to_mail_urls();
   $footnotes = '';