OK, bad news for you all. It is a bug in the create user script. But there is a way to fix this for the existing user. You need some basic SQL skills for this.
Open mysql and connect to the ox db:
This works only for the existing user. If you add more user, you need to do this again.
mysql> use open-xchange-db
mysql> update prg_contacts set intfield02 = null, intfield03 = null, intfield04 = null, intfield05 = null, intfield06 = null, intfield07 = null, intfield08 = null where fid = 6;