Merge two Microsoft 365 tenants, split one apart, or move a client between Microsoft 365 and Google Workspace. Mail and files are copied in passes while staff keep working, so the cutover only has to move the domain and the last changes.
The copying is much the same in all three. The planning decisions are different for each.
Usually after an acquisition. The first decision is which tenant survives. The second is what happens when both sides have a j.smith, an info@ and a team called Sales.
Colliding names, aliases and group addresses are settled in the plan before the copy starts. The acquired company's domain can stay on as an extra address, so mail to old addresses keeps arriving.
A business is sold or spun off and takes its people and data with it. SharePoint sites, Teams and shared mailboxes were built for one organisation and hold both sides' work, so they have to be picked apart.
Deciding exactly what leaves, and making sure nothing else does, is most of the job. Meanwhile the source tenant stays in daily use by everyone who isn't moving.
The data moves, but the formats don't match one to one. Gmail labels become Outlook folders, and a message with three labels has to land somewhere sensible. Shared drives become SharePoint libraries or Teams.
Google Docs, Sheets and Slides have no file to copy, so they are converted to Word, Excel and PowerPoint. Going the other way, folders become labels and Office files can stay as they are or be converted.
Copying starts long before cutover and repeats in passes. Each pass picks up only what changed since the last one, so the final pass is small and the cutover is mostly about the domain.
The inventory comes first: every mailbox, shared mailbox, site, team and group, the permissions on each, and the things that won't move as data. Accounts are then created in the target and the bulk copy runs while staff work as normal.
Copying early means cutover moves recent changes, not years of history.
Order matters. The domain is removed from every object in the source, verified in the target and added to the new accounts. MX and Autodiscover records are switched, the final pass runs, and mail is tested in and out before anyone signs in.
Each step is written into the runbook with how it's checked.
This is the part staff see. Outlook needs a new profile, OneDrive or Drive needs relinking, Teams or Chat needs signing in to the new account, and phones need the account added again.
It gets as much planning as the data, because it's where the client judges the move.
None of these are reported by the copy job. They turn up as tickets on the first working day.
What staff notice: replying to an email from before the move, or picking a colleague from Outlook's suggestions, returns a non-delivery report.
Exchange addresses internal mail by a legacy address that doesn't exist in the new tenant. Adding the old addresses to the new mailboxes as X500 addresses lets those replies land.
What staff notice: a shared mailbox has all its mail, but nobody can open it. The calendar is there, but the assistant can't manage it any more.
Delegates, Send As rights, calendar sharing and site permissions are settings, not content. They're recorded in the inventory and set again in the target.
What staff notice: scan-to-email, a line-of-business app or a website form stops sending and nobody notices.
Anything that relays mail through the old tenant, or signs in to it, is still pointed at the old service. These senders need finding before cutover, and DMARC reports afterwards show anything still sending the old way.
What staff notice: a supplier's link to a shared folder stops working.
Sharing links and guest access belong to the tenant that issued them. External sharing has to be set up again in the target, so the client should know who outside the business relied on it before cutover.
What staff notice: channel files are all there, but older conversations look different or aren't where they were.
Channel files live in SharePoint and copy well. Channel conversations and private chats are handled unevenly by migration tools, and Google Chat to Teams is different again. What moves, and in what form, is agreed before the work starts.
What staff notice: a Power Automate flow, a form or a Planner board isn't where it was.
Flows, Forms, Planner boards, app connections and mail rules that point at old addresses don't copy cleanly as data. The inventory names them, so the client decides what happens to each instead of finding out on the first morning.
Mail, calendars and contacts, personal and shared files, and team spaces, moved within the agreed scope.
Every cutover step in order, who does it, and how each one is checked before the next begins.
What moved and where it went, what didn't and why, and anything the client still has to decide.
We deliver the migration remotely as a white-label project, under your brand or as your named specialist partner, at a fixed price for the agreed scope. The client stays yours, and so does the support once they've moved.