Account Creation VS Domain Creation

I am totally new but purchased the PRO version.  My problem is when I create an account with the domain name input - say abc123.com for user admin1.  It is added successfully but I can't add the domain abc123.com due to record already existed.

OK, I delete the user to create the domain and it needs 1 username linking to it.

It is just likely an infinitely loop.  Currently, I am trying to use a dummy domain name for the user like abc123com with user admin1.  Then, I create the domain abc123.com with user admin1.

It should give me error for generation of SSL certificate.  Did I miss any vital step?  I am frustrated.   

if you create an account with domain abc.om then you already have that domain created as main domain of that account.
Domain adding is only for an additional domain to the existing accounts which is not recommended if not needed.

Thanks, understand.
I have tested & solved.  However, I would like to add more user under abc123.com and it will return "domain" already existed!

I added the user because I think the email box creation is linked to a particular user.  If I have multiple users to receive email, what is the right way.

Hi, it's impossible to use one domain with multiple usernames.

I don't follow the logic of one domain one user....what is meant by that?
I also use virtualmin control panel, and in virtualmin, I can assign as many users to client accounts as I want to.

Anyway, a workaround if your website is WordPress...add websites users in WordPress itself (These users don't need access to CWP)