“If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them.” The great Henry David Thoreau released Walden in 1854 about something completely different of course, but I am taking the liberty to use this quote in a cloud computing context. In almost every project I am in, I get this one question: Should we choose EM+S E3 or EM+S E5? And it really is a good question. The license cost is almost double in E5, and yet, the two licenses seems to contain a lot of the same stuff. Most of the time I can tell the customer what is gained by going for E5, but let’s look at some of the important differences here. Licensing can be extremely confusing, and Microsoft is in no way the worst company here.