ERROR (2): Header May Not Contain more than a Single Header, New Line Detected. (/webmail/inc/inc.php:169) [DirectAdmin]

If you see this error in /webmail:

ERROR (2): Header may not contain more than a single header, new line detected. (/webmail/inc/inc.php:169)

edit /var/www/html/webmail/inc/inc.php, go to line 169.
Change

Header("Expires: Wed, 11 Nov 1998 11:11:11 GMT\r\n".
"Cache-Control: no-cache\r\n".
"Cache-Control: must-revalidate");

Header("Expires: Wed, 11 Nov 1998 11:11:11 GMT");
Header("Cache-Control: no-cache");
Header("Cache-Control: must-revalidate");

Save, and exit.

Email to friend
* Your name:
* Your email:
* Friend's email:
Comment: