Messages can always be deleted (unless the company admin has switched this option off in the company settings). However, only the owner (read: sender) of the message can delete it.
A deleted message will be replaced with a message containing the text: “This message has been deleted by *NAME*”. When a message is deleted, it will be removed from all devices, including the devices of the sender, those belonging to the receivers and the Zaurus servers.
To delete a message on the web version, click on the recycle bin on the right side of the message.
To delete a message on a mobile device, press down on the message until a menu appears. In this menu click ‘Delete’.