OneDrive and other notifications

Credit goes to BitTitan for this solution.

The default mail routing can be manipulated by a mechanism called Criteria-Based Routing (CBR). Instead of dropping the mail in the mailbox on Office 365, we can intercept the message and transfer it to the original email system. The interception is based on criteria similiar to the membership of a specific Distribution List.

This is best explained by using the same example scenario:

• John was migrated to Office 365 in the first batch.
• Tom is part of a Distribution List (DL) called NotMigrated.
• We have set up a CBR mechanism that defines the following:
• If you are a part of the DL NotMigrated, your mail will be intercepted, and will be sent to the on-premises environment.
• This way, when John sends an email to Tom, it will not go into the Office 365 mailbox, but instead be transferred to the On-Premises Exchange 2010+ environment.

More information can be found here: https://technet.microsoft.com/en-us/library/jj950234(v=exchg.150).aspx

Step-by-step setup:
For the setup, use PowerShell, because it is faster and easier to set up than working through the Office 365 admin portal. If you need information about how to do this through the Office 365 admin portal, contact Microsoft Support.

1. Connect to Exchange Online PowerShell.
2. Create the Distribution List (DL):
   New-DistributionGroup -Name "BtNotMigratedUsers"
3. Add All Users to this DL.
4. Create the Connector:
   $result = New-OutboundConnector -Name "CBRConnector" -ConnectorType OnPremises -SmartHosts "<fill smart host to source environment>" -UseMXRecord $false -IsTransportRuleScoped $true
• Notes:
• -SmartHosts entry needs to be set to the URL or IP Address of the Source environment server.
• On Exchange 2003, 2007, and 2010, this will be the address of the Transport server.
• On Exchange 2013 and 2016, this will be the address of the Mailbox server, not the Transport server.
• If the Source environment is Hosted, you would need to obtain this address from the Hosted provider.
• If the Source environment is G Suite, you would need to change the -SmartHosts entry to be the following: -SmartHosts “aspmx.l.google.com”
5. Create Rule:
   $result = New-TransportRule -Name "PilotInABoxRule" -SentToMemberOf "BtNotMigratedUsers" -RouteMessageOutboundConnector "CBRConnector"

When a user is fully migrated, remove the user from the DL, and they will receive their email in their own Office 365 mailbox

Reference: https://help.bittitan.com/hc/en-us/articles/115008260168-How-do-I-set-up-mail-routing-on-Office-365-when-migrating-users-in-batches-