Office 365 Migration

Why do I need an on-premises exchange server for Office 365?

I’m just coming off an Office 365 email migration project, and once again, a question came up that I thought I’d address. To put it in very simple terms, clients are baffled why once their Office 365 email migration is complete, they still need to keep an Exchange server on-premises.

Microsoft Recommends Keeping an Exchange Server

In fact, Microsoft recommends keeping an Exchange server on-premises after your organization has migrated to Office 365 in case you have to modify mailbox properties such as email name changes, Proxy Address changes, etc. If you do not keep an Exchange hybrid sever around and approach Microsoft Support for help with any of the above scenarios, you will very likely be told that it is “not a supported configuration.”

What is “Not Supported” by Microsoft?

Let’s break down what exactly is “not supported”. Once you remove the last Exchange server, if you wish to add proxy addresses, edit email addresses, or modify other email-related attributes, you can technically do so using an ADSI Edit [adsiedit.msc] tool (Active Directory Service Interface Editor) or the attribute editor in ADUC (Active Directory Users and Computers). The only downside, in this case, is that you won’t have the user-friendly interface to edit the email properties of a user account, though several third-party tools fill that gap.

If you decided to contact Microsoft Support for help with editing an email address using either of these tools, you will get push back because Microsoft does not support manually editing the attributes. In other words, you must use an onsite Exchange Server to be able to call them up.

Office 365 Mail Flow is Still Supported

However, if you contact Microsoft Support with an email message that “is stuck” after you moved to Office 365, you will get support because your issue now is about mail flow. We have been in contact with Microsoft support for issues related to Office 365 (Exchange Online) mail flow when there was no Exchange server onsite and they have always helped us.

Editing an Office 365 Distribution List

One other issue that remains and does need to be addressed is the editing of Distribution Lists. It can be done, but it is a very difficult and technical process. Luckily, there are third-party solutions that address the problem.

Removing the Last On-premises Exchange Server

At iShift, we have developed a successful methodology to remove the “last Exchange Server” and not break Office 365 email. It has worked for many of our clients and has allowed them to simplify their IT environment while eliminating the need for additional Exchange licenses.

Office 365 Email Migration Help

If you are ready to remove that last on-premises Exchange server and be certain that nothing will break, Contact Us, and our certified Microsoft experts will help you through this last step of your Office 365 email migration.

Frequently Asked Questions

How do I ensure support from Microsoft even when I eliminate the last on-premises Exchange server post-migration?

Microsoft is committed to ensuring 99.9% email uptime no matter how big or small your organization is. When it’s about mail flow, they listen.

How long will decommissioning the last Exchange server following an email migration to Microsoft 365 using iShift services take?

This depends on the specificity of your environment. What we can promise you is that we will be in charge of the decommissioning of the server and will support you should any updates to your groups and distribution lists post-migration need to be performed.

Removing a legacy Exchange server(s) after a migration to Office 365 (Exchange Online)? Why it’s better to delete rather than decommission (uninstall) on-premises Exchange servers.

iShift has developed a best practice to handle this. We advise that Exchange server be disabled and shut off, NOT uninstalled. iShift will utilize MS tools to remove the server properties from Active Directory without damaging the Exchange attributes. This allows for you to still manage most properties/attributes related to mailboxes from on-premises Active Directory.

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Charles Arconi

About Chuck

Charles Arconi is a Principal Architect at iShift who has 25+ years of IT experience architecting and deploying cloud-based email and communication technologies. For the last 10 years, Chuck’s primary focus has been migrations: data to the cloud, email to Office 365, archiving data to cloud, etc. He is an accomplished technologist who likes direct interactions with clients, speaking, explaining, and strategizing about technology with them.

He also is a think-out-of-the-box kind of guy who likes to challenge mainstream practices and design innovative methodologies for the sake of efficiency, effectiveness, and usefulness. Every month Chuck will offer his take on cloud industry news, cloud-native technologies, and practices, and share his original insights about best practices in cloud computing. You can follow Chuck on LinkedIn or contact him directly at [email protected].

About iShift

iShift is a multi-cloud technology solutions company that provides cloud engineering, cloud migration, cloud management and specialized IT staffing services. Our mission is to help businesses to simplify and accelerate growth while enabling digital transformation and IT modernization. No matter where organizations are in their cloud journey, iShift can design, build, optimize and manage a future-ready multi-cloud environment, resulting in significant cost savings, increased workforce productivity, operational resilience, continuity of services, and business agility. For more information on how our offerings empower businesses through their adoption of cloud and modern technology, visit

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