ExpressPro option not visible during installation

During installation, MailSite ExpressPro is not listed under the installation options

MailSite ExpressPro 8.x and up to 9.4 requires Microsoft .NET Framework 2.0 to be installed on the server.
MailSite 9.5 requires Microsoft .NET Framework 4.0. If this is not installed, the MailSite installer will not show ExpressPro as an option.

Microsoft .NET Framework 2.0 and 4.0 can be obtained from the Microsoft website. Be sure to install the full version of the .NET Framework (rather than the client version)

After Microsoft .NET Framework has been installed, run the MailSite installer again and elect to install ExpressPro.

For instructions on how to install IIS, see KB 10221