Currently the full feature set of ESS (meaning the exchange part also) is not supported to be installed silently and unattended. It can be done in the means that you have already done, but there are certain pitfalls on the way such as the admin.pub workaround. Due to these pitfalls we do not support this method of installation on full ESS combo. The Server Security part can be installed silently and unattended with either Policy Manager and push installation or then by exporting .MSI package from PMC and using SCCM to install it.
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