We have 3 zimbra servers running with this intended use.

mailstore1 (1750 users/4TB storage)
mailstore2 (1750 users/4TB storage)
proxy perdition for imap/pop and tomcat for webUI ( intend 0 users)

We like giving a single URL for webUI use but I have the unexpected result of a full mail store that could have an account created on it by error. Is there a way to prevent account creation? (COS offers some control but it can be overridden manually)

I installed the mailstore because I think I need it to get tomcat.