Adding extended attributes for Kerio Connect Email Server

Does anyone have experience with using Kerio Connect with UCS?

Having a hard time added some custom extended attributes for our email server.
The email server is a Kerio Connect server and I found a Cool Solutions page on adding it but for Univention 3.2.

I've tried to follow the steps but don't understand how to add the custom extended attributes.
I'm not sure if it's a difference in the Univention version or if I'm just not understanding.
Kerio version is 9.2.1 and Univention version is current.

Thanks for any help or ideas

There is additional information about "Expansion of UMC with extended attributes" in the standard docs package. In addition it is possible to create these attribute on the command line as described in Develeper documentation: Packaging Extended Attributes .
The behaviour is the same in current UCS versions.

Thanks for replaying.
I contacted Kerio support and found out I could import users without modifying the Domain/LDAP Directory.
So that works even better for me.
Thanks again