In the Privacy settings on the website you can choose whether or not you wish to reveal that you have read a received message. The read receipts are activated as standard. In the XING apps you can deactivate these in the settings. This will then automatically be applied for all devices that you use your XING account from.
Please note: If you deactivate read receipts you will no longer be able to see whether your sent messages have been seen by the recipients either.