This error seems to be caused by a bug in php:
[Wed May 12 15:48:08 2004] [error] PHP Warning: fsockopen(): unable to connect to localhost:143 in /var/www/html/squirrelmail-1.4.2/functions/imap_general.php on line 454
Try recompiling everything from “clean”.
cd /usr/local/directadmin/customapache rm -f configure.* ./build clean ./build update ./build all /sbin/service httpd restart (or "/usr/local/etc/rc.d/httpd restart" for FreeBSD)