Office365 AD replication not working

I use Exchange Online Protection but all my mailboxes and mail-enabled contacts are all still in my on-premise exchange server. I setup AD replication, but some of my contacts have not replicated, so they are not receiving email.

Is email routing through Exchange Online protection completely dependent on AD synchronization? Can I create a connector in Exchange Online Protection that routes email to my exchange server without trying to resolve the recipient in AD first?
cyberleo2000Asked:
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cyberleo2000Connect With a Mentor Author Commented:
I found out from Microsoft that if you use any rules in EOP you need dirsync. The problem turns out to be internal to microsoft. Its a replication problems between the Office365 database and the Exchange Online Protection database.
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Gareth GudgerCommented:
I believe you can just turn off the AD Harvesting attack protection. Of course, not recommended. But then it will forward anything addressed to your domain to your mail server, regardless of whether it is a real address or not.
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cyberleo2000Author Commented:
But how do you turn it off?
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ontechCommented:
Directory Synchronization does not affects your email routing.

When you are using EOP, the Outbound connector is configured to move all emails to your exchange server. Check the connectors if configured correctly and move all emails to move to your on prem exchange server.

Dirsync only syncs AD attributes to Office 365.
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cyberleo2000Author Commented:
I resolved it by speaking to a Microsoft engineer.
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