Index: mail.inc
===================================================================
--- mail.inc	(revision 2715)
+++ mail.inc	(working copy)
@@ -421,8 +421,10 @@
  * Wraps words on a single line.
  */
 function _drupal_wrap_mail_line(&$line, $key, $values) {
-  // Use soft-breaks only for purely quoted or unindented text.
-  $line = wordwrap($line, 77 - $values['length'], $values['soft'] ? "  \n" : "\n");
+  if ($len = variable_get('drupal_wrap_mail_line', 77)) {
+    // Use soft-breaks only for purely quoted or unindented text.
+    $line = wordwrap($line, $len - $values['length'], $values['soft'] ? "  \n" : "\n");
+  }
   // Break really long words at the maximum width allowed.
   $line = wordwrap($line, 996 - $values['length'], $values['soft'] ? " \n" : "\n");
 }