Wiki notification emails with Kerio mail server on same box

We have Kerio Connect mail server (9.0.4) running on OS X 10.11 with Server 10.5 and can't get notification emails from Wiki to work. We have tried the suggestions for mail relay and manually editing the notifications.plist file (now restored to default) but with no luck.

Kerio had a previous support post about effectively pointing the server to the Kerio postfix location (http://kb.kerio.com/product/kerio-connect/os-x/enabling-php-s-mail-command-to-wo rk-with-kerio-connect-on-mac-os-x-272.ht…) but this no longer appears to work in OSX 10.11 - does anyone have any ideas or has managed to get this to work?