Hi Felix, nice to see you here. We was in contact back in the days from Zarafa Test Days. I will write you via PM on the Zarafa Forum 
Installing from repositories does not work in my case, since im on a Raspberry Pi. There are no official Packages for Z-Push, Zarafa or Kopano at Raspbian. I would be more than happy, to see a Repo for Raspberry Pi, official or not. I know, there are Packages for Arch Linux made by Pietma, but i didn’t like Arch Linux because of its Rolling Release Philosophy. If there is a Repo up, for Kopano or Z-Psuh, i would love to see the Address here.
If you have some ideas, how to tweak the settings a for Raspberry Pi, i would love to see your Feedback. Currently i fight with some Timeouts for the Ping Command and a small TimeZone Issue. Manfred have seen my Problems other there in the Zarafa Forum.