Combine two office 365 tenants - need help

Hi,

I need to combine two different office 365 tenants after a merger or acquisition. Our company X (250 users) has acquired another company Y (200 users), both companies have their on-premise active directories and both companies have already enabled Azure AD Connect to sync their AD users with Office 365 tenants for emails that means emails of both companies are in office 365 but in their own tenants. Using only mailboxes, no onedrive/sharepoint.

After google, found out no simple way to combine/migrate one tenant to another tenant and for this I would need to use Hybrid approach on either side ( would preffer on company Y side) for this migration. At the end, email addresses of company Y e.g Y.com will become X.com as primary and Y.com will be added as alias, main concern is to avoid re-configuring of outlook profiles of company Y users when their email domain will be changed to X.com in X tenant and also want to avoid computer domain login issues. Never done such migration before so looking for directions, can someone please provide guidance?

As for as I know, would need to move mailboxes downwords from 365 to one-premise exchange in Hybrid on Y side, cut off from 365 tenant then setup hybrid again with X tenant, right? what to do next? please advise.

Thank you in advance.

 

Question Info


Last updated October 7, 2019 Views 6,988 Applies to:

Hi MSITGEEK,

 

If these two tenants didn't set up Exchange hybrid and the mailboxes are pure hold online, you can follow the steps in this following article to migrate mailboxes from one tenant to another. And based on my experience, if you have no intention to set up Exchange hybrid in the future, there is no need to move mailboxes to on-premises Exchange servers. You may just follow the detailed steps in this article to complete the migration. And there are some things you do need pay attention to: 1. Please back up all your data such as use Outlook's export function in case data lost during the process. 2.To decrease the business impact to minimum, perform it during the weekend.

 

Besides, I'd like to confirm some information to further help you.

 

  1. Would you like to set up Exchange hybrid or you are hybrid scenario now?
  2. Would you like to use X.com as your domain or use both X.com and Y.com?
  3. Would you like to manage users in  separate ADs or under X.com AD?

 

Reference: https://support.office.com/en-us/article/how-to-migrate-mailboxes-from-one-office-365-tenant-to-another-65af7d77-3e79-44d4-9173-04fd991358b7

 

Regards,

Leo

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Thank you for quick reply, here are answers:

1. I do not want to setup hybrid, I mentioned it because I heard that is the only option for such migration?

2. When Y.com users will be moved to X.com tenant, their email addresses will be changed to X.com as primary but Y.com will be added as alias.

3. I'm really not sure, what are the options here?

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This really goes beyond Office365. This involves the merging of the computing resources of 2 companies.

I would assume, that both independent companies would have

1. Separate Authentication Servers (In this case each have their own AD Servers)

2. Separate IT policies and naming conventions

3. Separate Line of Business Apps (Finance, HR, ERP, Project Mgmt..etc)

4. Separate Security and Backup Systems

5. Separate Networks

6. Separate Productivity tools (Emails, Intranets, etc)

I would start by doing a detailed discovery and mapping out the IT systems of both companies and their dependencies.

Then decide how the merged environment would look. 

The discovery might also reveal how touching one system might affect the rest of the systems in the company.

Getting an experienced vendor/consultant to help you with this might be the way to go.

If you find my reply useful, would appreciate if you can click it as helpful.

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Hi MSITGEEK,

 

No, hybrid migration is not the only option, the article I provided above doesn't use hybrid migration. To help you better understand the differences between these, I will explain more: For hybrid migration, you can imagine it like using an Exchange on-premises server as a bridge ---- after it is setting up, emails can be routed to on premises servers, which enables you to cut off the online tenant with a low mail flow impact. Then you will gradually migrate your on-premises mailboxes to targeted Office 365 tenant.

 

The advantage of the whole process is it has a low impact to your mail flow, and on the contrary, as you can see in the article I provided, after changing the MX records of your domain, it may have a down time to restore according to TTL value and DNS transition time.

 

But with hybrid migration, it may have additional fees if you doesn't have Exchange server before, for example, you will need to buy licenses for using this service. And you can see the advantage of another method now ------ it may have lesser cost than hybrid migration and it is easier to perform, without the steps to move your mailboxes between on-premises and cloud.

 

So it depends on you which migration method you want to use, if you don't have a high demand for interrupt of mail flow, the method above seems a better option for you, otherwise you can choose hybrid migration.

 

Regarding the AD management option, what I suggest is using the method in the above article if you are not familiar with separate management, or you can use soft match to separately manage the two ADs.

 

Besides, please check Vincent's reply about carefully evaluate your services. Hopefully you can get your work done without encountering any issues during the process.

 

@Vincent, thank you again for helping our customers.

 

Some references:

 

  1. Exchange licenses: https://products.office.com/en-sg/exchange/microsoft-exchange-server-licensing-licensing-overview
  2. UPN soft match: https://docs.microsoft.com/en-us/azure/active-directory/connect/active-directory-aadconnectsyncservice-features
  3. Hybrid migration: https://support.office.com/en-us/article/use-minimal-hybrid-to-quickly-migrate-exchange-mailboxes-to-office-365-fdecceed-0702-4af3-85be-f2a0013937ef

 

Regards,

Leo

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Hi MSITGEEK,

Have you checked my reply? Feel free to let me know if you have further questions.

Regards,

Leo

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This really goes beyond Office365. This involves the merging of the computing resources of 2 companies.

I would assume, that both independent companies would have

1. Separate Authentication Servers (In this case each have their own AD Servers)

2. Separate IT policies and naming conventions

3. Separate Line of Business Apps (Finance, HR, ERP, Project Mgmt..etc)

4. Separate Security and Backup Systems

5. Separate Networks

6. Separate Productivity tools (Emails, Intranets, etc)

I would start by doing a detailed discovery and mapping out the IT systems of both companies and their dependencies.

Then decide how the merged environment would look. 

The discovery might also reveal how touching one system might affect the rest of the systems in the company.

Getting an experienced vendor/consultant to help you with this might be the way to go.

Thank  you Vincent for detail, you are right both are two different companys with their own ADs, domains and applicatons but both have their on-premise ADs synced with Office 365 tenants (their owns) for 365 emails. For now main concern is to move their emails into primary company's tenant and during this migration we do not want to distrub their computer logins, and cannot afford re-configuring outlook profiles for whole company. So what are the suggestions?

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Hi Leo,

Thank you for the directions. The link you mentioned says use third party tool? that means if we need tool then it's license cost will also be involved? Can we do this without third party tool and it's cost?

Actually, I want less problems during the migration and mainly why I think Hybrid is the preference because I do not want to re-configure outlook profiles for 200 users that is the main concern. And for exchange licensing cost, can we not use Exchange with trial? because we get 6 months trial I guess right?

And for example If I proceed with Hybrid, what would the steps to proceed with Y company mailboxes are moved to on premise exchange then what's next? Can  you please give some directions from here onwards?

Looking forward to hear from you.

Thanks

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Hi MSITGEEK,

 

Sorry for the delay, I was out of office in the weekend. If you already have an Exchange trial license, 6 months would be sufficient to complete the migration process.

 

And I will illustrate the framework of hybrid migration process:

 

  1. First you will need to create a migration endpoint to establish connection between your online service and your on-premises service.
  2. Then you need to enable MRSProxy service in EAC.
  3. After that you will need to run the migration wizard in EAC to move your mailboxes.
  4. After migration completed, remove batches.
  5. Re-enable offline access for Outlook on the web.

 

Here is a brief introduction: https://technet.microsoft.com/en-SG/library/o365e_hrcmoverequest_fl312271(v=exchg.150).aspx

 

And here is a more specific guidance: https://technet.microsoft.com/en-us/exdeploy2013/Checklist?state=3229-W-AAAIAAAAQAAIAAEAAAAAACAAAABEaAOFAAA~

 

Regards,

Leo

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Hi MSITGEEK,

Have you checked my reply? Feel free to let me know if you have further concerns.

Regards,

Leo

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