Email routing O365 Exchange

We have migrated an email domain from an Exchange 2010 server to O365. We have other email domains on this Exchange server. All external email is going fine to mailboxes in O365. Internal email originating from the Exchange server from other domains is not reaching mailboxes in O365 but still reaching their old mailbox on Exchange server.

I have hidden the mailbox of's users in Exchange, removed as Authorative domain from Exchange server, created a send connector to bypass anti-spam filter and send email destined for directly using MX record. But emails from other internal domains are still being recieved only on Exchange server not on  O365

Please advise any steps I can take to troubleshoot further

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Jason CrawfordTransport NinjaCommented:
You need to convert the migrated mailboxes to Mail Enabled Users and populate the targetAddress with the alias of the Office 365 mailbox.
abhijitm00Author Commented:
Thanks Jason. To convert them to mail enabled users do I need to delete their mailboxes on Exchange server to do this?
Jason CrawfordTransport NinjaCommented:
Someone already wrote a script for the entire process:

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Adam BrownSenior Systems AdminCommented:
Change from an Authoritative domain to an Internal Relay domain or make sure the users have their email address as a targetaddress in their AD Attributes (Jason Crawford's script should do this for you). Once users are migrated to O365, they should not have a mailbox on-prem. If the migration was done as a Hybrid Move instead of a cutover or staged migration, this should be done automatically.
abhijitm00Author Commented:
The script worked. Thanks Jason and Adam
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