While creating a new mail, Sogo searches my LDAP address books for the pattern. According to https://wiki.sogo.nu/ResourceConfiguration the pattern matching should be anchored: "when searching in addressbook, SOGo will search in mail, displayName, cn, sn and givenName where it will try to match strings from the beginning (ie 'me' will match 'meetingroom' but 'roo' won't match)".
I did a tcpdump while typing "cio" and recognized sogo is searching cio instead of *cio. So many more matches as expected are shown, not that bad ... but there are sideeffects of that behaviour. (see screenshot 1)

I subscribed a shared calendar of our CIO (cio@uni-koblenz.de). I want to create a meeting in his calendar inviting some other people. The availability dialog now shows the availability of the invited user and some other person (with "cio" in his givenname, Mauricio), but not the availability of cio@uni-koblenz.de. (see screenshots 2 and 3)

I think this is a bug. When inserting an appointment to a shared calendar, the owner of the calendar should be searched for exactly not just as a search for a part of his mail address.