@Reviles what exactly do you mean? There aren’t any limits on what Mail-in-a-Box can handle other than the hardware/VM limitations, but those aren’t an exact science. The limitations there have nothing to do with the configuration of the Mail-in-a-Box software itself.
I meaning best HW config. for XY users of mailinabox.
when I have 230 users of mailinabox, and 1VPS with 1c and 1GB ram - if mailinabox can works correctly.
When I have 500 users, 800 user - etc. etc. etc.
The problem with creating such guidelines is that they are not a straightforward matter. Not only would this take a significant time investment from either @JoshData or a member of the community, the results would be quite varied and dependent upon more factors than just the user and domain count. The better metric would probably be the use profile in terms of how many clients are connected at any given time and what they’re doing with the server.