How to Set-up Hybrid Microsoft 365 / Exchange Server Mailflow

by sircles on Mar 20, 2024
To keep a domain within Microsoft Exchange Server and Microsoft 365, you need to ensure that the domain is correctly configured for mail flow

To keep a domain within Microsoft Exchange Server and Microsoft 365, you need to ensure that the domain is correctly set up and verified in both environments. Here’s how you can do this:

For Microsoft Exchange Server

  1. Configure Domain in Exchange Server: Add the domain to your Exchange Server configuration. This is done through the Exchange Admin Center or via Exchange Management Shell, where you specify the domain as an accepted domain within your Exchange organization.

  2. Create Email Addresses: Assign email addresses with the new domain to your users. This can be done individually or by modifying email address policies to include the new domain.

  3. DNS Configuration: Ensure that your DNS settings for the domain point to your Exchange Server for mail delivery. This typically involves configuring MX records to direct email traffic to your server.

For Microsoft 365

  1. Add the Domain to Microsoft 365: In the Microsoft 365 admin center, go to the Setup section and select Domains. Follow the prompts to add your domain.

  2. Verify Domain: Microsoft 365 will require you to verify ownership of the domain. This is usually done by adding a TXT record to your domain's DNS settings. Microsoft will provide the specific value you need to enter.

  3. Update DNS Settings: After verification, you need to update DNS records, such as MX, CNAME, TXT, and possibly SRV records, to point to Microsoft 365 services. This ensures that services like email, Skype for Business, and others are correctly routed through Microsoft 365.

  4. Assign the Domain to Users: Change the user's email addresses in Microsoft 365 to use the new domain. This can be done individually or in bulk.

Considerations for Both Environments

  • Coexistence: If you intend to run both Exchange Server and Microsoft 365 simultaneously (in a hybrid configuration), you need to ensure proper coexistence settings are configured. This includes setting up directory synchronization and potentially full hybrid configuration with secure mail flow between the two environments.

  • DNS Management: You may need to carefully manage your DNS records to ensure that they correctly point to the appropriate services (on-premises or cloud) based on where the resources and users are primarily located.

  • Licensing and Compliance: Ensure that all users are appropriately licensed for the services they are using in Microsoft 365 and that you comply with Microsoft’s licensing terms.

By following these steps, you can successfully keep a domain within both Microsoft Exchange Server and Microsoft 365, ensuring smooth operation and email delivery for your users.

How do I ensure full hybrid configuration with secure mail flow between the two environments?

To ensure a full hybrid configuration with secure mail flow between Microsoft Exchange Server and Microsoft 365, follow these steps:

1. Prepare Your Environment

  • Verify Prerequisites: Ensure you meet all prerequisites, including supported Exchange Server versions, necessary licenses, and an SSL certificate for the Exchange hybrid deployment.
  • Update Exchange Server: Your on-premises Exchange Server should be updated to the latest Cumulative Update (CU) or at least the n-1 supported CU.
  • Directory Synchronization: Set up Azure Active Directory Connect to synchronize your on-premises Active Directory with Microsoft 365.

2. Use the Hybrid Configuration Wizard (HCW)

  • Run HCW: Download and run the Hybrid Configuration Wizard from your Exchange admin center. The HCW guides you through the steps needed to create a hybrid deployment.
  • Choose the Full Hybrid Configuration: This option configures a more integrated environment between your on-premises Exchange and Microsoft 365.
  • Configure OAuth: Follow the HCW prompts to configure OAuth authentication, allowing secure authentication between the systems.

3. Configure Mail Flow

  • Define Send and Receive Connectors: The HCW should help you set up the necessary send and receive connectors for secure mail flow between the environments.
  • Ensure TLS Encryption: Ensure that the mail flow between Exchange Online and your on-premises Exchange Server uses TLS to encrypt the messages.
  • Set up Edge Transport Server (if applicable): If you use an Edge Transport server, configure it to handle mail flow between the on-premises and online environments.

4. Validate the Configuration

  • Test Mail Flow: Send test emails between the on-premises and cloud mailboxes to ensure mail flow works correctly in both directions.
  • Verify Directory Synchronization: Check that user accounts, groups, and contacts are correctly synchronized between your on-premises Active Directory and Azure AD.
  • Check Free/Busy Information: Ensure that calendar free/busy information is correctly shared between on-premises and cloud users.

5. Monitor and Manage

  • Regular Monitoring: Monitor the mail flow and check for any security or performance issues regularly.
  • Update Policies as Needed: Adjust email routing, spam filtering, and transport rules as necessary to reflect changes in your organization's needs and security landscape.

6. Train and Support

  • User Training: Educate your users about the hybrid environment, focusing on any changes in email handling or calendar sharing.
  • Provide Support Resources: Ensure your IT support team is equipped to handle questions and issues related to the hybrid setup.

By following these steps, you can establish a full hybrid configuration with secure mail flow between your on-premises Exchange Server and Microsoft 365, allowing for a seamless integration of your email environments.

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