Attach and detach of mailbox

Reggie 20

We have an Exchange 2016 mailbox in an area which has a very slow link and we are unable to migrate this mailbox to 0365

What would be the best way to migrate with the least amount of downtime to avoid non-delivery reports ? Could we archive the contents of the mailbox to a pst, detach the mailbox, create a new O365 mailbox and import the PST?

Thanks

1 answer

Jake Zhang-MSFT 7,850 Reputation points Microsoft Vendor

2024-12-13T07:51:50.2933333+00:00
Hi @Reggie,

Welcome to the Microsoft Q&A platform!

Migrating an Exchange 2016 mailbox to Office 365 (O365) over a slow link can be challenging, but there are strategies to minimize downtime and avoid non-delivery reports (NDRs). Here are a few options:

A hybrid migration allows you to maintain both on-premises and online mailboxes, providing a seamless experience for users. This method is particularly useful for environments with slow links as it allows for a staged migration.

Minimal Hybrid Migration is a streamlined version of the hybrid migration, designed to be quicker and less complex. It involves verifying your domain, running directory synchronization, and migrating mailbox data in batches.

Your suggested method of exporting the mailbox to a PST file, detaching the mailbox, creating a new O365 mailbox, and importing the PST is also viable. Here’s a step-by-step outline:

Use the Exchange Admin Center (EAC) or PowerShell to export the mailbox to a PST file.

Set up the new mailbox in Office 365.

Use the Office 365 Import Service to upload the PST file to the new mailbox.

Cutover Migration involves migrating all mailboxes at once. It’s suitable for small organizations with fewer mailboxes and can be completed over a weekend to minimize downtime.

For larger organizations, a staged migration allows you to move mailboxes in batches over a period of time. This method reduces the load on your network and can be managed more easily.

Given your slow link, a minimal hybrid migration or staged migration might be the best options to ensure minimal downtime and avoid NDRs. These methods allow for a more controlled and gradual migration process.

Please feel free to contact me for any updates. And if this helps, don't forget to mark it as an answer.

Best,

Jake Zhang
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Reggie 20 Reputation points

2024-12-16T13:39:57.83+00:00

Thanks Jake

Could you provide the steps involved for a minimal migration?

Jake Zhang-MSFT 7,850 Reputation points Microsoft Vendor

2024-12-17T09:33:59.54+00:00

Hi @Reggie,

Certainly! Here are the steps for a Minimal Hybrid Migration from Exchange 2016 to Office 365:

Prepare Your Environment

Ensure your domain is verified in Office 365.

Make sure your Exchange 2016 server is up to date with the latest cumulative updates and patches.

Set Up Directory Synchronization

Download and install Azure AD Connect on your on-premises server.

Configure Azure AD Connect to synchronize your on-premises Active Directory with Azure AD.

Configure Hybrid Configuration

Use the HCW to establish a hybrid configuration between your on-premises Exchange and Office 365.

Ensure that mail flow and free/busy information are working correctly between on-premises and Office 365.

Migrate Mailboxes

In the Exchange Admin Center (EAC), create migration batches for the mailboxes you want to move.

Start the migration batches. Mailboxes will be synchronized to Office 365 while still being accessible on-premises.

Once the initial synchronization is complete, finalize the migration for each batch.

Update your DNS records to point to Office 365. This ensures that mail flow is directed to Office 365 and that clients can locate their mailboxes.

Decommission On-Premises Exchange (Optional)

Ensure all mailboxes and services are functioning correctly in Office 365.

If you no longer need your on-premises Exchange server, you can decommission it after verifying that everything is working as expected in Office 365.

Notes:

Perform the migration during non-peak hours to minimize impact on users.

Inform users about the migration schedule and any expected downtime.

Keep an eye on the migration process and be ready to address any issues that arise.

Please feel free to contact me for any updates. And if this helps, don't forget to mark it as an answer.

Best,

Jake Zhang

Reggie 20 Reputation points

2024-12-17T11:15:38.0866667+00:00

Thanks, could you also provide the detailed steps to detach a mailbox and attach the new O365 mailbox?

Jake Zhang-MSFT 7,850 Reputation points Microsoft Vendor

2024-12-19T09:31:47.4233333+00:00

Hi @Reggie,

Certainly! Here are the detailed steps to detach a mailbox from Exchange 2016 and attach it to a new Office 365 mailbox:

Export Mailbox to PST

Open Exchange Admin Center (EAC).

Go to Recipients > Mailboxes.

Click on More Options (...) > Export to a PST file.

Detach the Mailbox

In the EAC, go to Recipients > Mailboxes, select the mailbox, and click on More Options (...) > Disable. This will detach the mailbox from the user account but keep the data in the database.

If you want to completely remove the mailbox, you can use the Remove option instead of Disable.

Create a New Office 365 Mailbox

Navigate to the Office 365 Admin Center.

Click on Add a user to create a new mailbox.

Enter the required information to create the new mailbox.

Import PST to Office 365 Mailbox

Use the Office 365 Import Service to upload the PST file. You can do this via the Security & Compliance Center.

Navigate to Data governance > Import.

Follow the prompts to create a new import job and upload the PST file.

Once the PST is uploaded, map it to the new Office 365 mailbox.

Verify Mailbox and Update DNS Records

Ensure that the new Office 365 mailbox is functioning correctly and that all data has been imported.

Update your DNS records (Autodiscover and MX records) to point to Office 365 to ensure proper mail flow.

Please feel free to contact me for any updates. And if this helps, don't forget to mark it as an answer.

Best,

Jake Zhang

Jake Zhang-MSFT 7,850 Reputation points Microsoft Vendor

2024-12-24T01:56:31.7766667+00:00

Hi @Reggie,

Please kindly consider this comment as a warm follow up, I want to know if your problem has been solved. If you still have any other questions, please feel free to comment here and I'm glad to provide further support.If the above info is helpful to this question, you can click "Accept Answer". Have a nice day!

Best,

Jake Zhang
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Attach and detach of mailbox

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