in /var/www, there is a softlink webmail -> /usr/share/squirrelmail. browse http://localhost/webmail can go to the webmail login page. after setup drupal multisites (codebase in /var/www/site-1.com/web), add webmail -> /usr/share/squirrelmail softlink under both /var/www/site-1.com/web and /var/www/site-2.com/web and include /usr/share/squirrelmail in open_basedir in ispconfig 3 control panel, but can't access the webmail interface from both sites. why? how to solve it?