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Office 365 hyrbid configuration.

Hi All,

We’re in a process to push office 365 hybrid configuration wizard to configure Exchange hybrid.

1. Is there any way we don’t directly expose our on-Premises Exchange servers to office 365?

2. Is there any requirement to open port 25 or port 80, 443 between office 365 servers and on-premises Exchange servers?

3. Can we make change into send and receive connectors after ruuning hybrid configuration wizard. It creates for us?
What we’re trying to achieve here is — Office 365 —> smart Host —> Exchange on-premise!


Thanks for taking your time to respond...
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Ali-Raza111
Asked:
Ali-Raza111
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3 Solutions
 
timgreen7077Exchange EngineerCommented:
1. Is there any way we don’t directly expose our on-Premises Exchange servers to office 365?
No, you have to have an interfacing Exchange server unless you have some type of VPN connection between on-prem and Azure

2. Is there any requirement to open port 25 or port 80, 443 between office 365 servers and on-premises Exchange servers?
Ports 25 and 443 pointing to your on-prem Exchange server should be all you need.

3. Can we make change into send and receive connectors after running hybrid configuration wizard. It creates for us?
Yes you can modify the send connectors and receive connectors for hybrid.
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Ali-Raza111Author Commented:
Thanks for the response!
Just to clarify about modifying Send and Receive conmectors which would be automatically configured after running hybrid wizard.

Can we put smart host between office 365 and on-premises.
In order
office 365
Smart Host
Exchange on-premises.

2. Opening port 443 and 80 between office 365 IP's and on-Premises Exchange? Can you elaborate this ponit?
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timgreen7077Exchange EngineerCommented:
Yes you can add a smart host if you choose to in that order. We actually send traffic from Office 365 tenant to our inbound gateway which is hosted by a 3rd party (not O365) and from their into our on-prem exchage so it goes o365 > 3rd party hosted inbound gateway > on-prem exchange.


You don't need to do anything special for ports, as long as ports 443 and 25 are accepted by your firewall and forwarded to Exchange you will be fine. Those are the ports that O365 require and I'm sure those ports are already being forward to your exchange servers.
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MichelangeloConsultantCommented:
Office 365 and On Prem Exchange in hybrid configuration do initiate a TLS tunnel for secure mail flow; for that to happen, Office 365 needs to have access to your Exchange servers on port 25 usually.
The exact configuration depends on your on prem Exchange deployment i.e. you can have internet facing Exchange Edge Servers as TLS tunnel endpoints for secure mail flow.
I'm not aware of any requirement on port 443 on Exchange servers part. I assume you have a DAG behind a load balancer, so client accesses happen on 443 993 995 587 which will be exposed to the world ( and, consequently, to Office 365).

Usually no third party gateways are supported as TLS tunnel endpoints - that does not mean you cannot successfully use them, just that if you need support from Microsoft, you will probably be asked to remove any unsupported appliance which is managing mail flow
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