Exchange Online migration from separate hosted provider including AD sync.

Here's the scenario.  My client is migrating from a separate hosted Exchange provider to Exchange Online.  They currently have an AD infrastructure on-prem they want to sync to Office365 for SSO.  This situation isn't really covered by a Staged or Cutover migration, and I definitely don't want to go the IMAP route.  Any ideas?
LVL 17
Jason CrawfordTransport NinjaAsked:
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Manpreet SIngh KhatraSolutions Architect, Project LeadCommented:
Why dont you have the data to PST create Mailbox on Premises with proper configuration and then plan the migration ?

- Rancy
Jian An LimSolutions ArchitectCommented:
you can use migrationwiz (or skykick) to do so.

is their hosted Exchange provider integrated with their AD?

IF yes, you need to make sure you utilise the Nosync attribute and create the mailbox manually first, migrated the mailbox then do a big bang cutover on migration date.
Jason CrawfordTransport NinjaAuthor Commented:
limjianan - the current hosted provider is not syncing with their local AD.  Let me ensure I understand your suggestion correctly:

1. Initiate AD sync between local AD and Office365 using Azure AD Sync Tool
2. Synced users will create cloud accounts in Office365
3. Assign license to synced users
4. Using third party tool (Migration Wiz or Skykick) migrate mailbox data to Exchange Online mailboxes
5. Manually recreate DGs and perms in Exchange Online

What if I followed steps 1 - 3 then used a Cutover migration to move the data?  I'd like to avoid using a billable third party tool if possible.
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Jian An LimSolutions ArchitectCommented:
yup. you can do that as well.

but is all about user experience and size of your users/mailboxes.

As a consultant, I barely recommend cutover migration unless the user size/mailboxes is less than 50 users/200mb per users. (or "manageable")
because you won't know when all the emails have been migrated on day one.

For migrationwiz, what is can do a pre-migration sync (emails older than 30 days), then full migration on the cutover date. this provide you a cleaner and shorter cutover period

But it is your choice.
Jason CrawfordTransport NinjaAuthor Commented:
By Cutover I meant Staged so I can limit the source mailboxes to the one included in a .csv file.  I have a sandbox setup in this exact configuration so I'll post my results when testing is complete.
Jian An LimSolutions ArchitectCommented:
sure. when you do staged, please also make sure you have criteria based routing (i.e. if office 365 based user try to write to user in another end, it will need to go back to the original user not landed in office 365)

or make sure you create mailbox only when you needed.

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Jason CrawfordTransport NinjaAuthor Commented:
Staged didn't work because it could not write back the targetAddress attribute to the hosted Exchange AD.  The only way I could make the test migration work was with a third party migration tool, in this case I used Migration Wiz although Skykick is also an option.
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