There are 4 main ways to access Open-Xchange:
PC/Notebook browser : https://ox.domainame.com
Mobile device browser : https://ox.domainame.com
You can also access from https://domainame.com/webmail, after login, click on OX icon.
Connecting to OX via Outlook with Open-Xchange Oxtender2:
Refer to https://support.exabytes.com.my/KB/a3347/installing-and-using-the-open-xchange-updater.aspx?KBSearchID=0 (Updater)
Refer to https://support.exabytes.com.my/KB/a3346/installing-using-open-xchange-connector-microsoft-outlook.aspx?KBSearchID=0 (Connector)
Connecting to OX via Mobile Devices via Active Sync or Relevant Plugin:
Refer to https://support.exabytes.com.my/KB/search.aspx?categoryid=487&search=Open-Xchange+Avtive+Sync&type=0 which cover some of the major mobile OSes.