Hello

We are about to migrate three companies to a shared office 365 solution. We are taking the migration in steps.

First we are creating all of the users in office 365 and assign them a license. Then we change the mx-records to office 365 so new mails will arrive here. (users will still have access to old mailserver through webmail, to read previously mails.)

Last we are migrating mails to office 365 for all users, with a 3rd party tool. (some users has gmail, other users has Exchange 2010 on-prem)

For the users who allready got outlook 2010 installed and connected to a exchange 2010 on-prem, I need to change the profile to connect to office 365 - so they will startup with a blank mailbox, and start receiving new mails here when mx-records are changed.

• How can I deploy a new outlook profile - with new change settings to all outlook users?
• could i simply create autodiscover records for all mail domains, and rely on outlook to automatic connect to office 365 insted of exchange on-prem?
• how would outlook act if autodiscover is telling outlook to connect to office 365 insted of on-prem exchange, will it start to sync all mails from the local .ost to the (new) exchange/Office 365?

Best regards, Steffen.

It's not feasible to deploy an Outlook profile for Exchange Online.  What you could do is wipe out the existing profiles and let Autodiscover do its magic.  Or just tell users to create a new profile; there may be benefit to retaining connections to the old system during a transition.

As to what Outlook does, it depends on what it's connecting to before the switchover and how you do the switchover.  Outlook might automatically figure it out but it might not.  I wouldn't depend on Autodiscover the way you're doing the migration.  But it should be easy enough for you to test, no?

Hi,

According to your post, I understand that you want to know the outlook behavior when move mailbox from on-premises to Office 365.
If I misunderstand your concern, please do not hesitate to let me know.

Do you deploy a staged migration or a cutover migration? Heres the article about it, for your reference:
https://technet.microsoft.com/en-us/library/jj874018(v=exchg.150).aspx
https://support.office.microsoft.com/en-gb/article/Perform-a-cutover-migration-of-email-to-Office-365-9496e93c-1e59-41a8-9bb3-6e8df0cd81b4

Besides, we need change MX record to point to Office 365, ensure all email is being routed to Office 365 mailboxes.
Then we can configure an Autodiscover DNS record for your Office 365 organization to enable users to easily connect to their new Office 365 mailboxes with Outlook and mobile clients.
This new Autodiscover DNS record has to use the same namespace that youre using for your Office 365 organization.

For outlook client, it need repair outlook profile or re-create outlook profile to complete modification.

Thanks