Dual Mail Servers in Domain/Migration

[r8escjohn]

Hello,
I think I know where I need to go to address my migration issue but before I totally bork our entire setup I thought I would ask :->
Setup:
Migrating to Zimbra OSS 5.0.6 from very old Postfix system. Zimbra has been working super for the last 6-7 month or so and to make ease of migration easier have set up alias files in the older Postfix box so all of our users still receive mail at the original address of:
juser@domain.com

Alias listing on older box:
juser: juser@zimbra.domain.com

DNS Records:
IN MX 10 mail.domain.com (older box)
IN MX 30 zimbra.domain.com
mail.domain.com IN A x.x.x.1
domain.com IN A x.x.x.1
zimbra.domain.com IN A x.x.x.11

In Zimbra mailbox setup (Using Thunderbird in IMAP setup) have return address for accounts set to 'juser@domain.com'.
Now ready for my Zimbra box to start doing all of my mail and to have the older Postfix box stop doing mail (It will still be active as it is our main DNS box for now)

I 'think' I need to first dump the MX record for the older box in DNS and then follow the directions on wiki page:
ManagingDomains - Zimbra :: Wiki

Am I way off here?
Any assistance would be greatly appreciated!!:->

[phoenix]

Use a Split Domain set-up for your migration.