Office 365 hybrid deployment

steh88 31 Reputation points


Looking for some pointers if someone can help and point me on the right path. We are in the process of migrating to Office 365 using a hybrid deployment, something I have never done before so looking for a few pointers and to see if my thought process is correct.

We currently have an environment consisting of 4 exchange 2016 servers with all inbound/outbound mail going through a secure mail gateway. When we migrate we are going to have a mixture of mailboxes within Office 365 and on prem.

So in terms of mail flow I am assuming it will be www>mail gateway>Exchange >Office 365.

Were my confusion lies is with the connectors both within Office 365 and Exchange.

My thought process is this:

Office 365
Mail flow connector>From Office365 to Your organisation Email server.
Use the connector only when have a transport rule that redirects messages
Route email messages using MX record (As this currently points at mail gateway)

Mail flow connector>From Your organisation Email server to Office 365
Verify via external IP of email server

Create mail flow rule to redirect emails via the connector

On Prem Exchange
Keep connectors as they are as currently set to go through mail gateway

Is there a connector that needs to be configured within exchange to then send emails to Office 365 or does the hybrid config wizard configure this.

Microsoft Exchange Hybrid Management
Microsoft Exchange Hybrid Management
Microsoft Exchange: Microsoft messaging and collaboration software.Hybrid Management: Organizing, handling, directing or controlling hybrid deployments.
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  1. Joyce Shen - MSFT 16,646 Reputation points

    Hi @steh88

    HCW will help you create send/receiver connectors automatically which could make sure the mail flow between Exchange on-premises and Exchange online. After that, if you want to add third-party mail gateway, you could create send connector for it manually.

    The official document here introduces the connectors in detail: Set up connectors to route mail between Microsoft 365 or Office 365 and your own email servers

    And how the hybrid mailflow works: Transport routing in Exchange hybrid deployments
    Please note that: Don't place any servers, services, or devices between your on-premises Exchange servers and Microsoft 365 or Office 365 that process or modify SMTP traffic.

    Below related links will be helpful to you as well:
    1.Mail flow best practices for Exchange Online, Microsoft 365, and Office 365 (overview)
    2.Hybrid Exchange and third-party SMTP mail gateway

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