Full circle: On-premises Exchange to Microsoft 365 — and back again

In the digital age we are in today, “cloud” is the big buzzword. If you chat with IT admins, they are either migrating to Microsoft 365, in discussions to migrate, or have fully completed their on-premises Exchange to Microsoft 365 migration. But some companies have taken the leap and moved to Microsoft 365 only to want to migrate back to on-premises Exchange because they have had a bad experience or the company changed leadership. The other reason is because there are some things you cannot do in the cloud but can do on-premises, and they miss that kind of control. This brings up a question for companies that are migrating to Microsoft 365: Should you keep your on-premises Active Directory servers and Exchange environment just in case you are one of the companies that will migrate back from Microsoft 365 to on-premises Exchange?

Microsoft 365 to Exchange reverse migration


To migrate to the cloud takes time, depending on the size of your organization. The IT security team has to ensure the safety and security of users’ data and mailboxes, and lots of planning goes into doing this. The first question you may ask is, can I migrate back to my on-premises servers? Yes, of course, you can move away from Microsoft 365 back to your on-premises version of Exchange, which is most likely not supported anymore and out-of-date. This would mean that if you had a six- to 12-month project to move all documents, email, etc. to the cloud, it would most likely take you as long to move everything back. Change controls would also need to be reverted.

For those who migrated to Microsoft 365 and whose users are fully on Azure AD and Microsoft 365, do you keep your on-premises Active Directory servers and Exchange environment? It’s a Catch-22 situation, right? If we take a step back a few months when COVID-19 hit, a lot of companies started taking financial knocks. Some customers I dealt with have moved everything back to on-premises to cut back on costs (which they could do because they still had their on-premises servers), or they stuck with Microsoft 365 but downgraded the licenses. Other companies that were running hybrid Exchange moved user mailboxes back to on-premises and kept only a select few in Microsoft 365 to save on costs and also looked at the licenses and downgraded where they needed to.

On-premises still has great appeal

Microsoft 365: Exchange migration

Let’s go back to where we spoke about “in discussions” with migrating to the cloud. I have had clients look at what Exchange 2019, for example, offers and compared it to Microsoft 365 — forget about the fact that you cannot really compare — but in their minds, whether it’s a migration to Microsoft 365 or to Exchange 2019, they would rather stick to having everything on-premises as in that scenario cost is not a factor. However, the other problem is security. Many still don’t trust the public cloud and don’t want to expose information to the Internet, so for them, migrating away and removing on-premises servers will probably not happen.

I have had customers not keep anything on-premises as most employees work remotely. As they are on Microsoft 365, they would get large mailboxes and the latest Microsoft Office applications. So, there would be no need to outlay funds to buy new equipment and storage to cater to the new Exchange Server versions and powerful hosts, whether it’s VMware or Hyper-V to run those applications on.

Yes, I have not answered the question: Should you keep your on-premises Active Directory and Exchange Server? Unfortunately, there is no straight answer to this. No, because you don’t have anything dependent on Active Directory locally besides Exchange, and with regards to printers, you could set up a connector for your printers for scan-to-email or that application that needs to send mail on Microsoft 365. You could save the license costs for Windows running on your hypervisor as well as client access licenses (CALs) for Exchange. And maybe you don’t need that Visual Studio subscription (needed for Exchange 2019) anymore so you can save money there.

Microsoft 365 to Exchange on-premises: Senior management makes the call

But this call has to be made by senior management at your company. You, as an adviser to your customer or an IT manager, can give the pros and cons of moving everything to the cloud and getting rid of everything on-premises. There might/will be a “no” because you have older applications that rely on an Exchange Server with its local Active Directory, so the servers have to be kept. You could downsize the servers to maybe on one or two DAGs instead of 12 or 13. Yes, there are still applications out there that are dependent on Active Directory, and it has been coded that way.

For every 10 companies, six will probably keep their servers on-premises, and the other four will not. In some situations, it makes sense not to keep servers, but there might be that 1 percent that feels they have a backup plan if they ever need to move back because the servers are still there. Yes, they will be legacy servers, but clients say, “If it ain’t broke, don’t fix it.” It is amazing how many clients still run Exchange 2010 today with the deadline of support ending next month! But that is a discussion for another time.

To sum up the article, there is no definitive answer here when it comes to what to do with your Exchange Server when you are moving to Microsoft 365. At the end of the day, we need to support the customer or your own company with the decisions they make by staying in the cloud, migrating back to on-premises Exchange, or running hybrid Exchange with a few mailboxes in the cloud.

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