Microsoft 365 GCC High Migration
If you're a defense contractor handling CUI, you cannot stay on commercial Microsoft 365. CMMC Level 2 requires a FedRAMP High authorized cloud environment for storing and processing Controlled Unclassified Information, and for most small contractors using Microsoft tools, that means GCC High.
The migration is the single most disruptive part of the CMMC journey -- and the most technical. Every mailbox, every file, every Teams channel needs to move from one Microsoft cloud to a completely separate one. Your email addresses stay the same, but everything behind them changes.
We handle the entire migration so you don't lose a day of productivity. We've done this for small defense contractors and manufacturers, and we know where the gotchas are before they become problems. If you're working toward CMMC Level 2 certification, this is likely the first major technical step.
Why You Need GCC High
This is one of the most confusing parts of CMMC for small contractors, so here it is in plain English:
Regular Microsoft 365 -- the kind you probably signed up for through your IT provider -- runs in Microsoft's commercial cloud. That cloud is not FedRAMP High authorized. It does not meet the data residency, personnel screening, or access control requirements that DFARS 7012 and CMMC Level 2 demand for CUI.
Microsoft 365 GCC exists, but it also falls short. GCC meets FedRAMP High for some workloads, but it lacks the strict data residency and physical separation requirements that the Department of Defense expects for CUI. It was designed for state and local government, not defense contractors handling controlled technical data.
GCC High is the environment that checks every box. It is operated exclusively by screened U.S. persons. Your data lives in U.S.-only datacenters that are physically and logically separated from commercial infrastructure. It satisfies DFARS 252.204-7012, supports ITAR access controls, and meets the cloud infrastructure requirements for CMMC Level 2.
If your team uses email, SharePoint, Teams, or OneDrive to work with CUI -- and most defense contractors do -- this migration is not optional. It is a prerequisite for compliance.
What Actually Migrates
GCC High is a completely separate Microsoft cloud environment. That means this is not a simple settings change or license upgrade. Your data physically moves from one environment to another. Here is what that looks like:
Email (Exchange Online)
Every mailbox, calendar, and contact list migrates to GCC High. Your email addresses stay the same. Your team opens Outlook the next morning and everything is there.
Files (SharePoint and OneDrive)
All document libraries, folder structures, and file permissions move over. If your team stores drawings, specs, or contract documents in SharePoint or OneDrive, all of it comes across.
Teams
Channels and team structures migrate. Chat history has some limitations depending on the migration approach, which we will walk you through during the assessment so you know exactly what to expect.
User Accounts and Security Policies
Azure AD (now Entra ID) user accounts, groups, and conditional access policies are rebuilt in the new tenant. MFA enrollment, role assignments, and access controls are configured to meet CMMC requirements.
There are things that do not migrate cleanly, and it is better to know about them upfront. Third-party app integrations -- like your CRM connector or signature tools -- will need to be reconnected or replaced. Power Automate flows typically need to be rebuilt. Custom SharePoint sites with heavy customization may need manual work. We identify all of these during the pre-migration assessment so nothing catches you off guard.
Our Migration Process
We have done this enough times to know that a good migration is a boring migration. No surprises, no lost data, no Monday morning where nobody can get into their email. Here is how we do it:
Pre-Migration Assessment
We audit your current Microsoft 365 environment -- how many mailboxes, how much data in SharePoint and OneDrive, what third-party apps are connected, and how your team actually uses the tools day to day. We map your current licenses to what you will need in GCC High and identify anything that will need special handling.
GCC High Tenant Setup and Configuration
We stand up your new GCC High tenant and configure the core infrastructure. Domain verification, directory sync, and the foundational settings that everything else depends on.
Security Baseline Configuration
Conditional access policies, multi-factor authentication, data loss prevention rules, and audit logging -- all configured to meet CMMC Level 2 requirements from day one. This is where most DIY migrations fall short. Getting the migration done is one thing. Getting the security configuration right is another.
Pilot Migration
We migrate a small group first -- usually 3 to 5 people. This lets us validate the process end to end, catch any issues with specific mailbox configurations or file structures, and make sure everything works before we touch the rest of your company.
Full Migration
We migrate the rest of your users in batches, typically grouped by department. Each batch is scheduled to minimize disruption -- usually over a weekend or during off-hours. Your team gets clear instructions on what to expect and when.
DNS Cutover and Mail Flow Configuration
We switch your mail routing to point to GCC High. This is the part where your email address stays the same, but the infrastructure behind it changes completely. We handle the DNS records, verify mail flow, and make sure nothing gets lost in the transition.
Post-Migration Validation and User Training
We verify every mailbox, every document library, every Teams channel. Then we walk your team through anything that looks or works differently in GCC High. Most things look the same, but there are a few differences worth knowing about.
Typical timeline: 4 to 8 weeks from kickoff to completion, depending on your data volume and complexity. A 15-person shop with straightforward email and file storage is closer to 4 weeks. A 75-person contractor with complex SharePoint structures and multiple domains is closer to 8. Either way, we keep your team informed at every step.
GCC High Licensing -- What to Expect
We are going to be straight with you: GCC High licensing costs more than commercial Microsoft 365. The per-user monthly cost is higher because the environment is purpose-built for government and defense work with stricter operational requirements.
A few things to know about licensing:
- GCC High licenses are [INSERT PRICE RANGE] per user per month, depending on the plan you choose. This is separate from our migration services fee.
- You need a Microsoft partner who is authorized to sell GCC High licenses. Not every Microsoft reseller has this authorization. We work with authorized partners and can connect you.
- Not everyone in your company may need a GCC High license. If you take an enclave approach, only users who handle CUI move to GCC High. The rest of your team stays on commercial Microsoft 365 at regular pricing. For a 40-person company where 10 people touch CUI, that is a significant cost difference.
We help you map out exactly who needs a GCC High license and who doesn't, so you are not paying for licenses you don't need. We will give you a clear cost comparison during the assessment so you can budget accurately.
GCC High Migration FAQ
Need to Get Off Commercial M365?
Let's scope your migration. We'll assess your current environment, map what needs to move, and give you a clear timeline and cost estimate.
30-minute call. We'll map your migration path.
Not ready to talk? Read our CMMC gap assessment guide to learn what's involved.