If you are an IT Director or CIO managing on-premise Microsoft servers, you likely have a date circled in red on your mental calendar: December 2026.
Or maybe you don’t. Maybe you think you have plenty of time.
I’m writing this because, after overseeing 750+ migrations here at ClonePartner, I can tell you exactly what is going to happen over the next 18 months. The "2026 Cliff" isn't just about software updates stopping. It’s about a massive resource scramble that will leave thousands of companies stranded on vulnerable, unsupported infrastructure.
This isn’t fear-mongering; it’s math. The number of active SharePoint 2016, Exchange 2019, and Office Online Server (OOS) instances currently running on-premise vastly outnumbers the available migration consultants.
If you are planning to wait until mid-2026 to start thinking about moving your Dynamics 365 or SharePoint data to the cloud, you are already too late.
In this guide, I’m going to break down the exact timeline, the hidden risks of the "Do Nothing" approach, and why moving now—using an engineer-led approach—is the only way to guarantee your data survives the transition.
The Master Timeline: When Does Your Infrastructure Die?
Let’s cut through the noise. Microsoft loves to bury dates in TechCommunity forum posts. Here is the consolidated reality of what is going away.
The "Big One": December 31, 2026
This is the hard stop for the most critical infrastructure components.
- Office Online Server (OOS): If you host Excel workbooks, render documents in browser, or use Power BI Report Server (PBIRS) on-prem, this is the end. There is no OOS 2025. It’s over.
- Project Server 2016 / 2019: End of Extended Support.
- SharePoint Server 2016 / 2019: End of Extended Support. (Technically July 2026, but often lumped into the EOY planning).
The "Early Warning": October 14, 2025
- Exchange Server 2016 & 2019: Mainstream support ends. You enter the "Extended Security Update" (ESU) phase, which is code for "Microsoft charges you a fortune just to patch critical vulnerabilities."
The "Legacy" Cleanup: April 2026
- SQL Server 2012: If you are still running this on Extended Security Updates, the final plug is pulled.
Key Takeaway: By the end of 2026, the entire "On-Premise" ecosystem as you know it—Exchange for email, SharePoint for files, OOS for rendering—goes dark simultaneously.
The "Do Nothing" Option: Why ESU is a Trap
I often hear clients say, "Raaj, we’ll just pay for the Extended Security Updates (ESU). We like keeping our data in our own building."
I get it. At ClonePartner, we respect data sovereignty. It’s why we built our entire "Binary on VPC" migration model (more on that later). But relying on ESU in 2026 is a strategic financial error.
1. The Cost Multiplier
ESU isn't a flat fee. It historically doubles every year. You are paying a premium for a product that is essentially on life support. You aren't buying innovation; you are buying a stay of execution.
2. The "Brain Drain"
This is the factor nobody puts on a spreadsheet. Try hiring a SharePoint 2016 administrator in 2027. The talent pool is moving to Azure, Power Platform, and Microsoft 365. The engineers capable of maintaining your legacy on-prem servers are retiring or retraining. If your Exchange Server crashes in 2027, you won’t be able to find anyone to fix it—at any price.
The 3 Hidden "Gotchas" of 2026 Migrations
So, you decide to migrate. You look at your Dynamics 365 or SharePoint instance and think, "We'll just run a standard tool."
This is where the nightmare starts. Moving from On-Prem to Cloud is not a "Copy-Paste" operation. The architectures are fundamentally different.
Gotcha #1: The Storage Limit (The 10MB Problem)
On your local SQL Server, you might have terabytes of storage. You’ve been dumping 50MB PDFs, high-res images, and massive CAD files into your database for years.
Microsoft Dataverse (Cloud) is expensive. And it has strict limits. If you try to migrate a 50MB attachment from Dynamics On-Prem to Dynamics 365 Cloud using a standard tool, it will fail. The limit is often capped at 10MB for certain transaction types.
How We Fix This: At ClonePartner, we don't just shove data into the pipe. We write custom scripts that identify large files during the migration. We automatically offload them to Azure Object Storage (which is cheap and secure) and insert a link back into your CRM record.
- Result: You keep your files. You save money on storage. The migration doesn't break.
Gotcha #2: The Identity Crisis (Windows Auth vs. Entra ID)
Your on-premise SharePoint uses "Windows Authentication" (Active Directory). The Cloud uses Entra ID (formerly Azure AD). These users do not map 1:1 automatically.
- "DOMAIN\jdoe" is not the same as "john.doe@company.com".
If you use a drag-and-drop tool, you will end up with thousands of files where the "Created By" field says "System Account" because the tool couldn't figure out who "DOMAIN\jdoe" was. You lose your audit trail.
How We Fix This: We build a User Mapping Matrix before we move a single byte. We script the translation of user identities so that a file created by John in 2014 still says "Created by John" in the cloud in 2026.
Gotcha #3: The "Orphaned" Data
This is specific to Dynamics 365 Migrations. Imagine migrating a "Note" attached to a "Contact." If the Note arrives in the cloud 2 milliseconds before the Contact does, the system rejects it. "Parent record not found." The Note vanishes.
We use an "Upsert & Retry" logic in our code. If a record fails because its parent isn't there yet, we don't delete it. We queue it and retry. We guarantee highest level of data fidelity.
Why "Engineer-Led" is the Only Safe Way Out
There are two ways to handle the 2026 migration.
Option A: The Self-Serve Tool You buy a license for a generic migration tool. You assign it to your internal IT team.
- Pros: Looks cheap upfront ($50-$500/month).
- Cons: Your IT team (who are already overworked) has to learn the nuances of API limits, throttling, and data mapping. When it fails (and it will), they spend weeks debugging cryptic error logs.
Option B: The ClonePartner Way We are not a tool. We are an Engineer-Led Service. We have done this 750 times. We have built integrations for 500+ apps.
When you hire us, here is what happens:
- You do almost nothing. We take 95% of the burden. You just connect us to the servers.
- Zero Downtime. We write scripts that optimize read/write speeds. We recently migrated 2 million records over a single weekend. Your team leaves on Friday using On-Prem, and logs in Monday using Cloud.
- Security First (The Binary Method).
- This is our secret weapon. We know you hate sending data to third parties.
- We don't ask for your data. We compile our custom migration script into a secure binary.
- You run this binary on your own VPC (Virtual Private Cloud).
- The data flows directly from Your Source to Your Destination. It never touches our servers.
The Cost of Waiting vs. The Cost of Action
The laws of supply and demand are brutal. Right now, in 2024/2025, migration consultants have availability. By mid-2026, every company that procrastinated will be flooding the market. Rates will triple. Timelines will stretch. You will be stuck with "C-Player" consultants because the experts are booked solid.
Don't be the CIO explaining to the board why the company's data is stuck on an unsupported server in 2027.
Your Next Step: The "Zero-Risk" Assessment
We know you’ve been burned by vendors who promise the moon and deliver errors. That’s why we offer Unlimited Sample Migrations. We will take a chunk of your actual data—your messy, complex, real-world data—and migrate it to a test environment. We will do it again and again until you are satisfied.
Ready to beat the 2026 clock?
Book a Free Migration Strategy Call
Frequently Asked Questions