I came across the Autodiscover and Migration Issues post on the Migrationwiz.com Blog. It discusses a few options for working around Autodiscover issues when migrating between Exchange Orgs, typically to and from Hosted providers.
For some time now I have been using another method, which works very well and is great for longer term co-existence.
1. Setup DNS (private and public) for a sub domain on target Exchange Org and mailboxes. E.G. mail2.noak.es; autodiscover.mail2.noak.es; and email@example.com.
2. Migrate the data.
3. Convert firstname.lastname@example.org to a Mail User (strip the mailbox, retain proxyaddress etc) in the source Exchange Org.
4. Add the targetaddress (“External E-mail Address”) and proxyaddress Daniel@mail2.noak.es to Daniel@noak.es in the source Exchange Org.
This works because Autodiscover will fail on SCP records, but continue with other steps until it uses the targetaddress and will successfully connect to autodiscover.mail2.noak.es.
Below: Outlook 2010 using Autodiscover to resolve on an premise AD user to Hosted Exchange mailbox.
Below: Outlook 2010 configuration complete resolve to Hosted Exchange.
It is often easier to script this and working with the right suppliers this can be done. Both Cobweb and Migrationwiz.com have API’s available which we can use to automate most of the work. When combined with taking multiple passes (initial + delta) results in minimal disruption to end users.
With Exchange 2010 SP1 Hosting editions beginning to appear all of this will be taken care of natively with the addition of remote PowerShell using New-RemoteMoveRequest and user federation.