131 Continental Drive
Suite 305
Newark, DE 19713
United States
SCO 515, Third Floor
Sector 70, Mohali
Punjab, 160055
Follow Us on Social -

Configuring mail routing for hybrid migration scenarios in Microsoft 365



This article will help you configure mail routing during the hybrid migration process from your on-premises mail server to Exchange Online (Microsoft 365). This will ensure zero interruption for your mail flows when some of your user mailboxes will be On-premises while the others have been migrated to Exchange Online.


Today, we will cover a scenario where your organization has Exchange Server 2016 On-premises and are planning to migrate to Exchange Online (Microsoft 365) via the hybrid migration, without any 3rd party tools or services.

This involves the process of running the exchange hybrid configuration wizard.

For this scenario, centralized routing is disabled (centralized routing is recommended only for compliance requirements).


  • Migration Roster – We need a migration roster that will help us configure and maintain mail routing as the migration progresses.



Mailbox Type

Mailbox Size (GB)

Migration Date

Successful (Y/N)

John Doe



12th May 2021


Bill Gates



14th May 2021



  • Security requirements of Accounts – The accounts performing these operations needs to be exchange server administrators on the On-premises server and Exchange Admin Role in Microsoft 365
  • DNS access – The account must have access to the Public DNS for making changes to the MX Records
  • Security Groups – We would need a Mail enabled O365 Security Group for non-migrated users, which will be updated every time users are migrated to the cloud for configuring the mail routing.

Configuration Steps

Create a Send Connector

  • To begin with, we need to create a Send connector in the exchange admin center that will be used to route emails from M365 to your On-premises server. (Note: The Hybrid Configuration wizard will create the connectors for you by default. In case you want to make changes to the connector for TLS etc., you can either create a new connector or edit the existing one.)
    • Click on Add a connector on the next screen.
    • Select Office 365 under Connection from and the Connection to, should be set to Your organization’s email server and Hit next.
    • In the next screen specify the Name of the connector and Description (optional) and click Next
    • Ensure to select the option Only when I have a transport rule… and hit next.
    • Specify the smart host address or IP address of your on-premises mail server for routing.
    • In the next screen, ensure to enable TLS
    • Validate the email.
    • The summary of your connector should look something like this before you hit the create button.

Create a Transport Rule

  • We will create a transport rule to route mails from Microsoft 365 to your On-premises for all users whose mailbox is still in an On-premises environment.
    • Navigate to Rules under the Mail Flow section.
    • Click on the + option to create a new rule…
    • In the next screen click on more options
    • Chose the option – Apply rule if – The recipient… is a member of this group.
    • In the next windows search for the mail enabled security group that you have created for non-migrated users as per the prerequisites.
    • The next step would be to add the action to redirect the message to send connected we created earlier as shown below.
    • Hit the Save the button on the next screen to complete the rule creation.

Update the MX record to point to M365


Written By
Aneesh Kumar
Aneesh Kumar
M365 Solution Architect
peer reviewed By
JAsjit Chopra
chief executive officer
Graphics designed By
sanika sanaye
Creative Design Director
Recommended Content

Email Insights

Get the latest updates from Penthara right in your mail box.
Sign Up

LinkedIn Newsletter

Monthly updates, news & events from Microsoft to help  your business grow.
Subscribe To Newsletter

Leave a Reply

Your email address will not be published. Required fields are marked *

More From This Category

How to disable Focus Inbox in Outlook for All/Selective users in Microsoft 365

For many, the inbox is the command center for their day. It’s the way to keep track of what is going on and what needs to get done. Outlook’s Focused Inbox makes this process easier by helping you focus on the emails that matter most to you. It separates your inbox into two tabs—Focused and Other. Emails you need to act on right away are in the Focused tab, while the rest wait for you in Other.

Read More
Generating detailed Microsoft 365 migration report for individual users in a batch via PowerShell

If you are looking for a way to monitor and report the progress of your Microsoft 365 mailbox migrations, this blog is for you.You will learn how to use a PowerShell script that can generate detailed migration reports for individual users in a batch. You will be able to see the status of each mailbox, whether it is completed or in progress, and save the reports for future reference. This will help you to keep track of your migration project and communicate effectively with your stakeholders.

Read More