EOP license for on premises users in a full hybrid



I have a question to ask.
I have to implement a full hybrid solution with an exchange 2016.
I will have some users on o365 and some users on premises.
I will point the mx record to the EOP services.
The o365 e1 licenses for users on o365 already have EOP licenses.
Since records mx also aims for on-premises users, do I have to purchase EOP licenses for these users too?
If I don't purchase EOP licenses for users on premises, will the emails be discarded and not delivered?

Thank you



3 Replies
Best Response confirmed by pazzoide76 (Contributor)

I think you don't need to. According to article Move mailboxes between on-premises and Exchange Online organizations in hybrid deployments - What do...


The Microsoft 365 or Office 365 Exchange license must be assigned only after the migration is complete. You then have 30 days to assign the license.


I think the license is for the Exchange Online mailboxes only once it is migrated. For the mail flow going in-and-out of your on-premise Exchange Server, HCW (Hybrid Configuration Wizard) automatically creates an inbound and outbound connector in Exchange Online Admin Center for your Exchange Server. 


Also this might help: 

For general overview of Exchange Hybrid, you can refer to Exchange Hybrid deployments.

For prerequisites of Exchange Hybrid, you can refer to Hybrid deployment prerequisites.

For mail flow, you can look into Transport routing in Exchange hybrid deployments.





thanks for your answer.
My doubt is that in the article it is said:
Route incoming Internet messages through the Exchange Online organization
The following steps and diagrams illustrate the inbound message path that occur in your hybrid deployment if you decide to point your MX record to the EOP service in the Microsoft 365 or Office 365 organization. The message path differs depending on whether you choose to enable centralized mail transport.
You may need to purchase EOP licenses for each on-premises mailbox that receives messages that are first delivered to EOP and then routed through the Exchange Online organization. Contact your Microsoft reseller for more information.



Hello, I will have to keep both users on premise and on o365.

I won't migrate all users.