I have been looking for something similar for years, and finally found a solution. What I was looking for is exactly what mailscape does; monitor and report on the performance of your Exchange servers and users. Mailscape also provides alerts if there are any issues such as mail queue overflows, or if a user fails to login due to a network problem. You can also use the built-in reports to determine where resources are being used. The only issue is that the pricing model is quite expensive (around $500 per month), but this allows you to see everything in detail. I would recommend anyone looking for a replacement for Mimecast to try this software. It’s worth the money.