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Plenty of growing organizations reach a point where they move from Google Workspace to Microsoft 365. The reasons vary: some want the full Office desktop apps and Teams, some are standardizing with clients and partners who already live in the Microsoft ecosystem, and some need the device management and conditional-access controls that come with the Microsoft stack. For government contractors there is an added pull, since much of the CMMC tooling, the assessors, and the managed providers in the defense space are Microsoft-centric, which makes Microsoft 365 the path of least resistance. (Not a requirement: Google Workspace can be made compliant too. The surrounding ecosystem just tends to be Microsoft.)
Whatever the reason, the decision is the easy part. The migration is where the real work lives. Here is what it actually involves, and where it tends to go wrong.
A migration is not a like-for-like email swap. Microsoft 365 is an integrated suite, and the real value is the pieces working together under one login and one security model.
Teams, chat, video meetings, and calling in one place. Most companies consolidate here and drop the separate spend on Zoom, Slack, or a standalone phone system.
SharePoint, a genuine company intranet and document hub: granular permissions, version history, and secure sharing with outside partners like a client, an auditor, or your CPA, without scattering files across a mess of shared drives.
OneDrive, every user's files synced, backed up, and recoverable, under the same controls as everything else.
The full Office apps, desktop Outlook, Word, Excel, and PowerPoint, licensed and installed for the people who need them.
Entra ID and Intune, identity, device management, and Conditional Access from one admin center: require MFA, restrict access to trusted or managed devices, and enforce the controls that frameworks like CMMC and HIPAA expect, without bolting on third-party tools.
The point is not that Google lacks equivalents. It is that in Microsoft 365 they are one integrated platform under a single identity, which is what makes both the daily work and the audits simpler.
1. Discovery. Before a single mailbox moves, you reconcile reality: who is actually active (we routinely find dozens of new hires and departures the org chart missed), how big each mailbox is, and every alias, forwarding rule, and shared mailbox in use. The surprises that derail cutovers are almost always found, or missed, here.
2. Licensing and provisioning. Right-size the licenses so you are not overpaying. Most staff need a low-cost mail plan, not the premium suite, and a handful need full Office or device-managed tiers. Then accounts get created and configured.
3. Pre-staging. Mail, calendar, and contacts get copied into Microsoft 365 while everyone keeps working in Google as normal, and kept continuously in sync. Done right, this phase is invisible to staff. No disruption and no frozen period.
4. Cutover. The weekend switch: update DNS records (MX, SPF, DKIM, autodiscover), run a final sync to catch the last messages, and flip the domain over to Microsoft 365. When it is planned properly, the only thing users notice Monday morning is a one-time login prompt.
5. Enablement. Every user signed in, MFA set up, shared mailboxes mapped, and someone to call when they are stuck. This is where migrations are won or lost in the eyes of staff.
The hard part is never the email itself. It is the edges: shared department mailboxes that were really separate logins and have to become proper shared mailboxes; app and device accounts like payroll systems, copiers, and scanners that quietly send mail as your domain and break at the DNS switch if no one catches them; autodiscover and DNS caches that keep pointing Outlook at the old provider for an hour after cutover; and the crucial difference between a mailbox that is synced and one that is actually finalized.
None of these are hard to handle. But every one of them is hard to handle after the cutover instead of before.
We recently moved a roughly 100-person organization, about 125,000 messages across the company, from Google Workspace to Microsoft 365 with zero data loss and no business interruption. Not because the tools were magic, but because every one of those edges was mapped during discovery and rehearsed before the weekend, not discovered live.
The worst time to migrate is in a hurry: mid-audit, mid-deadline, or after something has already broken. A deliberate migration, planned weeks ahead with mailboxes pre-staged and synced, turns the cutover into a non-event. A rushed one turns it into a Monday full of help-desk tickets and missing email.
KaselTech plans and runs Google Workspace to Microsoft 365 migrations end to end, from discovery through enablement, with zero downtime and no lost mail. Get a free migration readiness assessment and we will map your environment before anything moves.