It's really not appropriate for a business to come to a community forum intended for consumers and manned by volunteers or Microsoft contractors at best to ask a question about a large business software audit, as the answer you received should confirm.
However, since I at least have a medium sized business IT background and the ability to use search, I'll do my best to start you down a more sensible path.
The following Microsoft.com page provides information regarding both an "audit" and Microsoft Software Asset Management (SAM) voluntary action.
License Compliance Verification FAQ | Microsoft Volume Licensing
Note also that the email you received mentions the following:
"MACK ENERGY CORPORATION has been selected by Microsoft to complete a License Augmentation Review."
Beyond the fact that clicking that License Augmentation Review link takes me to apparent advertising for Microsoft products including the Surface Book 3, the title of that link alone should give you pause.
What is a License Augmentation Review? Possibly an attempt to sell you additional software you don't need (or possibly do) under the premise that you're going to be audited? And combined with the fact you noted that the company mentioned is obviously not an "Independent, internationally recognized certified public accounting firm" as mentioned in the License Compliance Verification FAQ, this all sounds just as suspicious as you inferred above.
So what I'd do is take a much more careful look at that email using a good email client that exposes the true address rather than the "friendly name" that many crappy email programs display and verify that it actually displays Microsoft.com rather than some convoluted one. Or if you understand how, look at the message source if using Outlook.com or a similar Microsoft product to see the true delivery pathway displayed in the headers to see whether, as is likely, the email address itself may have been spoofed.
In other words, to me this message is clearly fake and not how I'd expect a professional company to contact me in any case, instead likely using an official, snail mail letter on letterhead of the accounting firm assigned by Microsoft.
This is clearly a scam, possibly just trying to sell software, but also maybe intended to acquire your firm's or your own identity information for identity theft.
Rob