When using Enterprise Application Access (EAA) in a RDP session, there is a maximum screen resolution provided by two different RDP engines:

• The older engine inherits the properties of the browser window. For example, if your browser window is 800x600 when the session is started, it will retain that property. To change the resolution, restart the session with the browser window opened larger (or smaller) to alter the size. The older engine does not have the ability to support dual monitors.
• The newer engine has an interface that lets each client alter the resolution and other properties. The maximum resolution is limited by the RDP server version on your Windows server. This Microsoft Technet article discusses the resolutions supported by their servers:

  https://social.technet.microsoft.com/wiki/contents/articles/31983.remote-desktop-protocol-maximum-supported-resolutions.aspx

  The new engine is more efficient with system resources such as RAM.