Exchange admins who have installed Exchange 2010 using the command line will be familiar with the Setup.Com, which was part of the 2010 ISO/DVD. It doesn’t exist in Exchange 2013!
In Exchange 2010, we used setup.exe to install the product using the GUI and Setup.Com to install it from a command line.
So, how are we supposed to run the setup from command line in 2013? I can hear you asking 
. Well, the answer is really simple. In Exchange 2013, the setup.exe is used for both purposes – installing from the command line and using the GUI. There is no setup.com file in 2013.
A new parameter named /IAcceptExchangeServerLicenseTerms should be used while running Setup.Exe from a command line. Unlike other parameters which can take an abbreviation (MT for management tools), this license acceptance parameter has to be typed in full. Hence, in order to install the mailbox role of Exchange 2013 on a server, the following has to be run from a command line or as part of a script.
Setup.exe /mode:Install /role:Mailbox /OrganizationName:OrgName /IAcceptExchangeServerLicenseTerms
In short, setup.com is gone and all we need is setup.exe
