If you have a personal subscription, Microsoft makes it easy to grab the image file directly from your portal: Log into your account at Microsoft's download page . Select .
Unlike the standard setup file (usually 5-10MB), which acts as a download manager, the is a full ISO image or a large executable file (typically 3.5GB to 5GB) containing the 32-bit or 64-bit versions of the suite. office 365 offline installer exclusive