some issue on all-inkl.com
but after ignoring this message by changing index.php?_step=1 to index.php?_step=3 I could test the socket connection with an refused on ssl and an php_error without ssl (but the socket connection was successful)
Fatal error: Call to undefined function decrypt_passwd() in /www/htdocs/mail/nightlymail/program/include/rcube_smtp.inc on line 105
so I change to the latest svn-version and theres no socket warning in the installer (theres no point socket ;-) )
but again the problem with decrypt_passwd()
so try the latest svn version, maybe it works