I'm following the recommendation in WIKI to use pop2imap to migrate from sendmail to Zimbra but it's now working see below;

[root@BTVMfedora bin]# pop2imap --host1 mail.greatgulfhomes.com --user1...

Doing a new installation.

What is /opt/zimbra/data used for?

How much disk space does it need?

I read the documentation and the only directories I was worrying about are;
...

Looks like this is a common question that never gets an answer but I'll try.

I want to set-up 2 MTA servers to handle the incoming and outgoing emails.

How do I load balance the email traffic...

I'm setting up a new Zimbra server virtual environment for 800 mailboxes with a maximum size of 6 GB per mail box.
The attachment size limit is 20 MB due to sending ACAD drawings back and forth....