People,

I wonder what could be the caveats or things to consider before migrating my on-premise Exchange Server 2010 SP3 mailboxes into Office 365 at the end of this year the total Exchange Mailbox count is 2890 and total Mailbox database size is 8.5 TB.

My clients are using Outlook 2010 & 2013 (multiple Active Sync devices) spread across multiple geographical region site offices (Europe and Asia Pacific).

Note:

         I also have emails older than 1 year archived by Symantec Enterprise Vault 10 with approximate size is 7 TB
         Single AD domain forest.


My goal after migrating to Office 365 is to achieve the following:

1. No need to worry about Microsoft Exchange Updates, Hotfixes, updates and bugs with Active Sync devices (Delegate calendar nightmare).
2. Release the disk space used by the email infrastructure back to the existing Storage Array for another VM to use.
3. No need to worry about any outage or reliability issue at all.

Any thoughts and comments would be greatly appreciated.

Thanks in advance.

Once the email has been migrated to Office 365, can I decommission all Exchange Server on Premise ?

or do I need to keep some of the Exchange Server to keep email flowing ?

Based on your mentioned situation, I would strongly recommend you to follow Exchange server deployment assistant that is available from Microsoft team and covers all the required aspects by checking the necessary prerequisites : https://technet.microsoft.com/en-us/office/dn756393.aspx

Here is another informative technet article with the same concern and provides step-wise details to accomplish this task in flawless manner : http://blogs.technet.com/b/exchange/archive/2013/03/06/updated-exchange-server-2010-deployment-assistant-for-exchange-2010-sp3-and-office-365.aspx

In addition, if you are still concerned about users mailbox migration, you may look into this proficient application (http://www.exchangemailboxmigration.com/) that provides a hassle-free environment in order to get the migration job done without having downtime or any further interruption.

Based on your mentioned situation, I would strongly recommend you to follow Exchange server deployment assistant that is available from Microsoft team and covers all the required aspects by checking the necessary prerequisites : https://technet.microsoft.com/en-us/office/dn756393.aspx

Here is another informative technet article with the same concern and provides step-wise details to accomplish this task in flawless manner : http://blogs.technet.com/b/exchange/archive/2013/03/06/updated-exchange-server-2010-deployment-assistant-for-exchange-2010-sp3-and-office-365.aspx

In addition, if you are still concerned about users mailbox migration, you may look into this proficient application (http://www.exchangemailboxmigration.com/) that provides a hassle-free environment in order to get the migration job done without having downtime or any further interruption.

Hi Torsten, thanks for the repky and suggestion. So do I still need to keep some of the Exchange servers running on premise or I can completely decommission it from my environment ?

WHat about the email archive migration to Office 365 ? is there any tool to help with?

Based on your mentioned situation, I would strongly recommend you to follow Exchange server deployment assistant that is available from Microsoft team and covers all the required aspects by checking the necessary prerequisites : https://technet.microsoft.com/en-us/office/dn756393.aspx

Here is another informative technet article with the same concern and provides step-wise details to accomplish this task in flawless manner : http://blogs.technet.com/b/exchange/archive/2013/03/06/updated-exchange-server-2010-deployment-assistant-for-exchange-2010-sp3-and-office-365.aspx

In addition, if you are still concerned about users mailbox migration, you may look into this proficient application (http://www.exchangemailboxmigration.com/) that provides a hassle-free environment in order to get the migration job done without having downtime or any further interruption.

• Marked as answer by Senior System Engineer 5 hours 31 minutes ago

Hi,

If you move all mailbox, public folder and mailflow to Office 365, the Office 365 without on-premise Exchange can works fine. However, you can remain an on-premise Exchange server with all role. More details about "How and when to decommission your on-premises Exchange servers in a hybrid deployment", for your reference: https://technet.microsoft.com/en-us/library/dn931280(v=exchg.150).aspx

For archive mailbox when migration to Office 365, please refer to: https://support.microsoft.com/en-us/kb/2757430

Thanks

Hi Allen,

What about the email backup ?

If all email items are in the cloud (Office 365) so how do you back it up or restore when the users wants to retrieve back their email ?

Hi,

For your question, you can refer to below link to get answer:
https://community.office365.com/en-us/f/158/t/8935

"Just to confirm what the others have already said, your options for backing up mailboxes would be to export them to a .pst, or you can use the Hybrid Deployment scenario to control where your mailboxes are stored, so that you could move them back to your on-prem environment.  In this case you don't need to worry about backups of the mailboxes hosted on Office 365, as we provide that backup for you.  Even in the event that we're in a disaster recovery scenario, we guarantee the continuity of your data."