I'm searching for a solution to sync contacts and calendars in standard clients for desktop and for mobile. It's really unbelievable that nowadays an open source project remains monolithic without allowing a connection from outside. With opener 6 I was able to sync with caldav and carddav procedure. I was also able to use an external imap server different for each user. Actual interface is wonderful, but the software is missing a lot of features believing to be the only place where users must connect. I can be wrong, so I'd like to learn how to get those connections working, since they are necessary to use properly any kind of erp.