Migrating from on premise Exchange to Office 365

gopher_49 used Ask the Experts™
We plan on migrating 70 users from on premise Exchange to Office 365.  The on premise will stay on the domain for a few weeks after the migration.  Below are the steps in general I plan to do.  I have a few questions.  

Is there a way to automate the removing of the old profile and adding the new one that will point to Office 365?  I'm trying to void logging into each desktop if possible.

Is there anything else I need to do to make sure Outlook doesn't try to connect to the old Exchange server?  It has to stay online for while after the migration...

Start the migration in roll ups from On Premise to Office 365 (while that's running start the below steps)
Schedule the last roll up to be done Sat evening
Then change public DNS to point to Office 365.  Then change the public autodiscover records and private autodiscover records to point to Office 365 for their domain.  
Log into each desktop, delete old profile, add a new one with a different name.  (see about a method that will automate this)
Configure profile to access Office 365 account (assuming there isn't an automated way)
Set Outlook instances that support selective offline cache to only sync back 3 months.  We can later change if desired.
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Adam BrownSenior Systems Admin
Top Expert 2010

If you have a Hybrid configuration set up with your OnPrem Exchange, the migration is fairly easy to do. You don't have to do anything to Outlook profiles *as long as they are using autodiscover*. If you have manually configured the Exchange accounts, you will need to delete the existing account and create a new one in each profile. There's not really an easy way around it. There may be some scripts that will work, but it's been a while since I've done those, so I can't say for sure.

Once you migrate the mailboxes and re-home autodiscover records to Office 365, Outlook will properly configure things and your users will be able to connect to the Office 365 mailboxes without any changes to Outlook (Usually. Sometimes you have to repair the profile or recreate it). They will be prompted for credentials the first time and they just need to put in their Office 365 Creds. If you're using a Hybrid setup with ADFS, their username and password won't change. If you're using ADConnect with password sync, they'll have to use their email address as their username, and that's about the only difference. In a hybrid environment, everything that Outlook needs to find and connect to the mailbox is synced to the cloud, so as long as Autodiscover is already configured prior to migration and all outlook clients are using it, you don't need to do much of anything for Outlook to keep working after migration.
Systems Engineer
Top Expert 2016
Fairly easy is relative to the version of Exchange that is installed on premises.  If Exchange 2010 or newer, yes, it's a fairly easy process, like Adam states.

Basically these are the high-level tasks...
  • Add domain to O365
  • Update UPN suffixes for all AD accounts with a mailbox
  • Install AAD Connect (on server other than Exchange) and sync AD accounts to O365
  • Configure Exchange server for hybrid
  • Move mailboxes

Using this hybrid migration method allows a seemless transition for your Outlook users as the continuity of the existing profiles remain intact--PST files, Outlook rules, signatures, autocomplete (name cache), OST.

However, using directory sync with password sync does not make the users use their email addresses as their username.  In fact they have to use their on premises "user logon name" (which looks like and email address ... jdoe@contoso.com) just like a default AD FS configuration.  But if the user logon name is the same as the email address that is a huge bonus because the user doesn't have to learn something new.  The way users logon to O365 is no different with ADFS versus directory sync with password sync.  The difference is where the authentication occurs.  ADFS is on premise, while directory sync with password sync is in O365.

Alternately for mailbox migrations, you can move your mailboxes using third party tools offered by companies like BitTitan, Binary Tree, and SkyKick.  Some are inexpensive and some are not.  Some reconfigure the Outlook profile seemlessly and others do not.  Really, the biggest difference with these tools is cost and the ability to easily divorce Exchange from your on premises environment.

Good luck.  Have fun.  And let us know what you pick and/or if you need additional assistance or guidance.
E ATech Lead
With a hybrid migration there is no need to recreate it because your local Exchange server is integrated with Exchange Online and so it can redirect the mailbox. Users will just get prompted after migration that something is changed and that they need to restart Outlook.

Move mailboxes between on-premises and Exchange Online organizations in hybrid deployments:

For exchange server to office 365, you may take help from Microsoft Exchange Server Deployment Assistant which is a web-based tool that asks you a few questions about your current environment and then generates a custom step-by-step checklist that will help you deploy different versions of Exchange Server for different types of scenarios.

You may also get help from Office 365 migration solution for migration easily and efficiently.

However, a cutover migration is the simplest way to get all your existing email into Office 365. As the name implies, it’s a cutover from one service to another. Cutover migrations are supported for Exchange 2003, 2007 and 2010; for organizations with fewer than 1000 mailboxes. The process is pretty straightforward, however, be sure to properly test the migration plan prior to trying to implement.

Hope this helps!
Todd NelsonSystems Engineer
Top Expert 2016

FYI... With a cutover migration you will typically have to visit each machine to manually update/recreate each Outlook profile.
Hi Gopher,

If you want to get a clear idea of what the move to the Cloud could look like, check out Conversational Office 365 Migrations by J.P. Bruzzese.

You can download it for free from our website: http://www.codetwo.com/office-365-migration/pdf-guide/?sts=6549

Good luck!


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