Hello, We use zimbra 8 single server install in my company, but now we're expanding and we are planning to switch to multi server install.

I have read the multi server install guide and not all things are clear to me.

Does Zimbra Proxy act as an load balancer?

Usage scenario: Zimbra Proxy is on mailcluster.domain.tld, MX records for domains a.tld and b.tld are set to it. We want to have two separate mailbox servers for those domains.
Can Zimbra proxy server as an imap/pop/web server for it? We want to enable people from multiple domains to access their webmail/pop/imap on one domain(subdomain) if possible.

Do we need equal number of Mailbox servers and MTAs
It would be best for us to have each domain have it's own separate mailbox servers. Does each Mailbox (Store) server has to have its own MTA?