I am evaluating Mail-in-a-box for several use cases in SMB market like 150 to 500 mailboxes for companies in the business to business market.
Also I have a client, a small university that need 6000 mail boxes.
I normally deploy in AWS but can do it on a data center but always on virtual environment, so I can assign computer, memory and storage as needed.
My question #1 is: How big Mail-in-a-box can be in terms of quantity of mailboxes. Can support heavy load?
Question #2: Can I set up a cluster or any highly available servers farm?
Question #3: Can I get eventual or permanent support service,
Question #4: Is there any version that uses MySQL or PostgreSQL for big deployments?
If I deploy this software I plan to contribute ($$) for any commercial deployment I have.