M365 merging tenants

[autumn]

G day all

Currently looking at merging 2 existing M365 tenants. Both existing. And looking for help of the best way.

tenant 1, I'm unsure how much control I will have as this will be given to me, this tenant is the head office which has another IT company involved.
tenant 2, currently controlled by us, it was it's own business/business name, now HO wants all site to be the 1 brand,

Tenant 1 is a totally unknown structure or setup,
Tenant 2, about 20 users, a couple of meeting rooms, 5 or 6 sharepoints/temas to worry about

I think we will be heading down the following

Creating the users/teams in Tenant 1, leaving tenant 2 as mailbox only accounts, creating alias of the tenant 2 addresses in tenant 1, point all mail for tenant 2 to tenant 1.

The Mangaing Director of tenant 2 is happy to start afresh with mail, but I know down the track they will go, "I need something from my old mailbox". I am think PSTing them but is there another solution? I think I might have an issue with Teams historical as well.

I haven't move M365/Teams before or merged (I know it's not merging), so any gotcha's I need to watch for would be good.

And just to add to it, I'm coming off the back of bronchitis for 12 weeks, so not thinking well.

I'm planning not doing at the moment, eta 4 to 6 weeks away.

 

[Sky-Knight]

Pick a tenant, that's the one you keep, the other you migrate.

Merging tenants means three things... to start.

1.) User Data, Mailbox, personal OneDrives, and ultimately email address.
2.) Corporate data, SharePoint Sites & Teams.
3.) Platform data, Intune configuration, Conditional Access policies, actual endpoints (desktops, laptops, mobile devices, etc)

then there's 4... anything in Azure that uses the Entra tenant in question for authentication.

Scoping and pricing 1... easy... get a mailbox count.
Scoping and pricing 2... a little more complex... may require ShareGate or something similar, but MigrationWiz's file migration works too for some customers...
Scoping and pricing 3... hardest play by far, it's easy to move Intune Policies around, but consolidation of Conditional Access Policy takes some thinking, and moving the endpoints themselves is just a dead lift.

Azure... complete hairball, some stuff can migrate, other stuff needs redeployed, it all needs tested.

Oh, and you know what M365 licenses are required to support any and all of the above right?

Good luck...

This is a $15 - $30k project as described, just rough numbers off the cuff. And the argument over access? Yeah... that matters, and may have a contract in the way.

 

[YeOldeStonecat]

As I read the post...
*Tenant 1....managed by another IT company
*Tenant 2....your "current" client...

Business of "tenant 2"....is being bought up, or merged, by business of "tenant 1"?

And "Tenant 1" (managed by the other IT company)....will be the one and only tenant moving forward.

My gut tells me the other IT company would be doing this, since they are absorbing your current client (probably soon to be their client).

But yes a migration won't be too bad, todays migration tools make it quite easy. Even the native Microsoft built in tools can get it done...but I do prefer 3rd party tools.

Like Rob said above...the mailboxes...."migrate" is easy peasy. No need to "leave the old behind" and "start from scratch"...it's very easy to migrate the mailboxes (which include contacts, calendar, notes, etc). Migration tools that pre seed and do multiple delta sweeps keep away the potential of MIA email during cutover and greatly shorten the time needed for actual cutover.