Symptoms
Open-Xchange was installed and configured as per https://kb.odin.com/121621
Webmail account was created, however, the option "mobile devices support" doesn't make any difference in the OX webmail interface.
Cause
Open-Xchange packages, required for mobile devices support functioning are missing.
Resolution
Make sure that Business Mobility Installation Guide is followed correctly for your corresponding OS.
Install the following packages:
yum install open-xchange-eas-provisioning ox-updates-backend open-xchange-eas-provisioning-gui ox-frontend open-xchange-eas-provisioning-sms open-xchange-help-usm-eas