I have just set up caldav (davical) and ldap (openladp) on my Ubuntu server and was surprised to find how easy it was.
It would be nice if the two applications were supported - one for network calendering, and the other for addressbook storage.
Davical requires postgresql and php which are available for BSD and most flavours of Linux.
Openldap again is supported in Linux and BSD.
Squirrelmail, (and Roundcube which I tend to use) both support ldap address books as do a number of other mail clients and handheld devices.
Caldav is supported by a number of mail clients including Thunderbird and iCal (also worth noting native support on IOS and app support for Android).
All that is missing if a Caldav web client.
A small authentication plugin could be written for davical to allow it to authenticate against the ispcp email users database which would auto-create the davical user. I am not much of a coder, but it doesn't look too complicated.
Openldap could be configured without too much difficulty, it would probably require a) Initial setup b) the generation of an LDIF file which would be imported at domain creation time constructed from form data and c) another at email address creation time - see this url for info on how this works:
https://help.ubuntu.com/10.10/serverguid...erver.html
Am I over-simplifying things and not seeing the big picture?
As I have mentioned, I am not much of a coder, so although I could probably have a go at writing this, my code would by no means by elegant, and I would likely be buggy, poorly written and would make a rather more experienced programmer cringe.
Any thoughts?