I have read through the split domain article which for me seems to be overkill for my environment. Here is what I want to do:

1. Bring up new ZCS Network addition in the same domain as current mail server, set the MX to a lower priority.

2. Create a few mail accounts that do not reside on the primary mail server for testing purposes. It is my understanding that if an account does not exist on the primary MX mail server in a single domain, delivery will be passed along and attempted to the secondary MX server. Am I correct in this assumption of how MX's work? If this is true, I can effectively test the new Zimbra server fully for a period of time while the original mail server is still in production. This is really my biggest question.

3. After I am satisfied with test results. I plan to lower TTL on public MX records to something like a minute.

4. I will then create all accounts on the Zimbra server to match the original mail server.

5. Make DNS changes after business hours one evening.

6. Point everyone's mail client settings to the new server the next morning.

Our environment consists of less than 30 users and is currently using a POP3 mail server is my reasoning for this method. Of course, I will need to follow up with each user and import the local .pst files into Zimbra after migration. What am I missing here? Any gotcha's that will get me? Thanks in advance.