Forum Discussion
Azure AD before Exchange migration?
Hello. I am working on a plan to migrate an organisation from on-prem Exchange 2007 to Exchange Online. I want to set up Azure AD to sync passwords. There are only about 170 mailboxes so I was ...
My company does these fairly often with customers, doing a cutover migration when they have dir sync.
The big thing to know BEFORE you run the sync is that you need to do a custom setup of AADC and you need to ignore the ms_exchangeGUID attribute when you sync.
If you do not, O365 will think the users already have mailboxes, and you will not be able to provision blank mailboxes for them.
If you have already ran the sync, then you need to disable dir sync, delete the users, purge the users from deleted users, then re-run the sync with the ms_exchangeguid attribute ignored.
If you have any questions feel free to ask or message me directly! While this is not "supported" by Microsoft I have seen this done many times and can talk to you about the positives and negatives if you want to feel more informed before moving forward.
The big thing to know BEFORE you run the sync is that you need to do a custom setup of AADC and you need to ignore the ms_exchangeGUID attribute when you sync.
If you do not, O365 will think the users already have mailboxes, and you will not be able to provision blank mailboxes for them.
If you have already ran the sync, then you need to disable dir sync, delete the users, purge the users from deleted users, then re-run the sync with the ms_exchangeguid attribute ignored.
If you have any questions feel free to ask or message me directly! While this is not "supported" by Microsoft I have seen this done many times and can talk to you about the positives and negatives if you want to feel more informed before moving forward.
Thanks, Adam. Very informative. If you could clear one thing for me: when you say ‘ignore the ms_exchangeguid attribute when you sync’, do you mean apply optional filtering in AAD Connect? If so, would you mind providing a couple of instructions?
Thanks.
Hi,
We have dir sync with 200 users in Exch2010 server, now we want to migrate to O365 exch online
Tried to uninstall AD sync but somehow all users were still in Azur Dir
What should i do next?
Thanks
Adam Ochs wrote:
My company does these fairly often with customers, doing a cutover migration when they have dir sync.
The big thing to know BEFORE you run the sync is that you need to do a custom setup of AADC and you need to ignore the ms_exchangeGUID attribute when you sync.
If you do not, O365 will think the users already have mailboxes, and you will not be able to provision blank mailboxes for them.
If you have already ran the sync, then you need to disable dir sync, delete the users, purge the users from deleted users, then re-run the sync with the ms_exchangeguid attribute ignored.
If you have any questions feel free to ask or message me directly! While this is not "supported" by Microsoft I have seen this done many times and can talk to you about the positives and negatives if you want to feel more informed before moving forward.
