Alternatively you can try this one, IF you have a relay server in your network. It can then be configured completely from the admin gui..
=> your main domain (notesserver) is domain.com
=> create a zimbra domain zimbra.domain.com (no mx or so needed)
=> create an internal dns-record for zimbra.domain.com on your internal DNS-server
=> convert 'some' notes users to zimbra using wizard
=> import them to zimbra.domain.com
=> give zimbra users a canonical address
user@domain.com (now all outgoing mail will be from
user@domain.com)
=> create zimbra.domain.com on your frontend relayserver (=spam/av-filter), next to domain.com
=> relay your outgoing mail through the relayserver (it will route internal-mail between the two mailservers)
=> put a forwarding rule for all messages on the incoming messages for your zimbra-users on their old notes-accounts.
Now your users can transparently mail eachother and you can step by step migrate your users to zimbra. The incoming mail will be in both places whilst migrating.
Once finished migrating change the ip for domain.com to your zimbraserver, create domain.com on zimbraserver and move your users to domain.com.
Finally put your notes-server to sleep or use it a little more if you have specific notes-applications running on it.
This is how we are migrating (part of our domains, not all of them :0)). Of course this only works because we already had a spam/av-filter in place and not too many users to migrate at once.
Only drawback we noticed is absence of domino-directory/incomplete gal which is acceptable because of zimbra's feature of remembering mailed addresses.
Great plus is the possibility to experiment/fiddle with a conversion for specific users or repeat it if necessary giving the user the opportunity to check/clean his old/new mailbox/choice of clients and switch between the two whilst remaining 'productive' as in receiving and sending mail to others. We were pretty happy with this whilst working/waiting with/for the broken importwizard in 5.0.1...
Maybe this helps you or someone else.
Cheers,
Peter