How to migrate Exchange public folders to a shared mailbox in Office 365

This article shows, step by step, how to easily migrate Exchange public folders to an Office 365 shared mailbox using CodeTwo Migration software. The article also contains a guide on how to create a shared mailbox in Office 365 and how to access it from a mobile device.

Why migrate public folders to a shared mailbox?

You might wonder why should you even bother. How is this migration better than a straightforward transition to the target server public folders? There are two reasons why you might prefer shared mailboxes over public folders:

  • You can easily access shared mailboxes via a mobile device
  • They can let you save money, as shared mailboxes do not require separate licenses in Office 365

Public folders have been used to store important clients’ data for a long time now. Thanks to them, you can have important files and data stored in one place. All or chosen employees can then access public folders data from their computers. The problem is, to access this data on mobile devices, you will need a third party tool, like CodeTwo Exchange Sync.

With shared mailboxes, you can access data from shared mailboxes using Outlook on the Web and mobile Mail Apps.

Still, the most important part is that using shared mailboxes can let you save money. As you can learn on Exchange Online Limits page, a shared mailbox does not require a license. In other words, as long as you keep each of your shared mailboxes’ size under 50 GB and do not want to enable In-Place Archive or a Litigation Hold, you can reduce the number of licenses for your Office 365 tenant.

The tutorial consists of three parts:

  1. Create a shared mailbox on the target Office 365 tenant
  2. Migrate public folders to the shared mailbox
  3. Access shared mailbox

How to create a shared mailbox in Office 365

You can use three methods to make a new shared mailbox in Office 365: via a dedicated shared mailbox Admin Center, using Exchange Admin Center, or by entering a PowerShell cmdlet.

How to create a shared mailbox using Microsoft 365 Admin Center

Although I prefer to perform most administrative tasks using PowerShell, creating shared mailboxes seems to be easier and quicker with the Admin Center. Here is how to do this:

  1. Login to your tenant as a global administrator and go to your Admin Center. Then, choose Groups > Shared mailboxes in the left pane.

how to create shared mailbox in Office 365 1

  1. A list of existing shared mailboxes will appear. I have not added any shared mailboxes yet, so it is empty. Click Add a mailbox.

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  1. Here, you can specify the displayed name and email address of the new shared mailbox. Fill both fields and confirm by clicking Add button

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  1. The newly created mailbox should appear on the list. Now highlight the mailbox and Edit the members section.

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  1. Now, you can specify members who will have access to the resources you are about to migrate.

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This way, you have created a Shared Mailbox in your Office 365 tenant. You can also achieve the same result using Exchange Online Admin Center:

  1. Access your Exchange Admin Center > recipients > shared

Create Shared Mailbox in Exchange Admin Center 1

  1. As you can see, the shared mailbox I created earlier is visible here, To add another one, click the plus icon.

Create Shared Mailbox in Exchange Admin Center 2

  1. Similarly to the previous method, you can choose the email address of the mailbox and its Display name. Clicking the plus icon lets you choose which users will have the permission to this mailbox and resources it will contain. If you want to enable all users to access this mailbox, just click on a single user, press Ctrl + A key combination, and add them to the list. Confirm with the OK.

Create Shared Mailbox in Exchange Admin Center 3

How to create a shared mailbox using PowerShell

Even though I prefer to use the UI for this task (it just seems to be quicker), there are some situations in which you have to use PowerShell. For example, the reason you might want to use a cmdlet here is that this is the only method to set a Send on Behalf permission.

New-Mailbox -Shared -Name "Info" -DisplayName "Info" -Alias Info | Add-MailboxPermission -User [email protected] -AccessRights FullAccess –InheritanceType All | Set-Mailbox -GrantSendOnBehalfTo [email protected]

The cmdlet creates a shared mailbox [email protected] with the Display Name “Info and assigns full access rights to [email protected] The last part is optional and grants the Send on Behalf permission for the same user.

How to migrate Exchange public folders to a shared mailbox in Office 365

CodeTwo Office 365 Migration is an awarded software which makes a transition from an Exchange Server to Office 365 much easier than by native means. The program lets you perform a secure migration and use features such as filters, scheduler and detailed reports, which let you plan the whole process and leave it to finish automatically. Migrating public folders to the target shared mailbox using CodeTwo Office 365 Migration is also simple:

  1. Start from creating a new migration job from Exchange Server (or Office 365)

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  1. Begin the configuration by typing a descriptive job name

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  1. Next, connect to the source server (if you have not done this yet), and choose your public folders for to migrate.

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  1. The next step is to connect with the chosen target server.

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  1. After establishing the connection, you have to match mailboxes. Click Match mailboxes… to access a separate matching tool.

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  1. In the tool, match your public folders with the target destination manually.

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  1. Enter the target shared mailbox address, click OK, save changes in the matching tool and continue to configure the job. In the following steps, you can choose e.g. when to migrate your public folders and which item types to include. This configuration depends entirely on your environment, and you can modify it freely. Just remember that license-free Office 365 shared mailboxes are limited to 50 GB of space, so you might want to split your public folders into a few batches to migrate all content.

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  1. After configuration is finished, you can start the migration job manually from the Jobs tab:

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When the migration finishes, you will have an Office 365 shared mailbox which will contain emails, calendars, tasks and any other items you chose to migrate. You can find them in a folder named like your public folders, all in the target shared mailbox.

How to access shared mailbox in OWA

Automapping feature (turned on by default) will let all users with the right permissions access the shared mailbox in Outlook as easily as their own. Opening the mailbox in OWA requires users to perform an additional step:

  1. While in the Outlook on the Web, right-click on your name in the left menu, and choose to Add shared folder… from the context menu.

how to access shared mailbox in outlook on the web 5

  1. In the window that appears, choose the shared mailbox, and it will show up on the folder list.

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You can also get to the shared mailbox by clicking your name in the top-right corner and selecting Open another mailbox…

A window similar to the one in step 2 above will appear, and you will be able to choose the mailbox to which you have full access. This method is, by far, less convenient than the first one, but it works.

How to access a shared mailbox on mobile devices

Accessing shared mailbox on mobile devices can be achieved in the same way as on PCs if you use a mobile browser (tested on Chrome) to access Outlook on the Web. You might need to open the browser’s settings to request desktop site of the website and add the shared mailbox using the method described above. After that, you can go back to the mobile version and the previously added mailbox will remain.

As for now, mobile Outlook Apps do not support opening shared mailboxes. It means that you can either use the method above or configure a native mail app manually, with the following details (To access those settings you need to go to your device’s settings screen and add a new email account):

  • Email: shared mailbox address, e.g. [email protected]
  • User Name: your email address followed by the shared mailbox alias, e.g. [email protected]\sharedmailbox
  • Password: your password.
  • Incoming server:, Security type: SSL/TLS, Port: 993
  • Outgoing server:, Security type: TLS, Port: 587

Such configuration should enable you to access your shared mailbox easily, as long as you have the right permissions set.

Further reading

Tools for Microsoft 365

12 thoughts on “How to migrate Exchange public folders to a shared mailbox in Office 365

  1. Hi,

    I might have a question or two about public folder migration. It is said we need 100 licences for migrating publics folder to M365.

    My goal is to migrate about 250GB of PF to shared mailboxes, so it will fit in 5/6 shared mailboxes. Is the required licences number still 100 or do i need to plan 100 licences for each shared mailboxes ? It might seems like a stupid question, but i’d like to make sure.

    Also second question, for the migration do i have to just follow this guide then repeat it as much time as i need with different sources folders and destination mailbox ?

    And the last one, i assume that you can just select which public folder you want migrate and not necessary all at once, can you confirm me that ?

    • Hi Florian,

      The migration of public folders always requires 100 licenses – this number is fixed and doesn’t depend on the actual size or number of migrated public folders.

      Regarding your second question: With CodeTwo Office 365 Migration, you can set up the migration process according to your needs. You can configure a single migration job to migrate all items (in one go or in specific time frames thanks to the built in Scheduler), or you can set up multiple migration jobs to move specific items when necessary. For a step-by-step guide, refer to the user’s manual.

      Regarding your last question: Unfortunately, it is not possible to select which public folders should or should not be migrated, but you can exclude specific public folders from migration using this method.

  2. hi there, sorry if this isnt the right place to ask this, but this is the closest Ive found… is it possible to migrate an existing source server user mailbox over to a destination shared user mailbox ?

    thanks in advance for any guidance

    • In CodeTwo Office 365 Migration, you can use a CSV file to provide matching information, as described here. If you have any additional questions, our Customer Success team is available 24/5 and will be happy to assist.

  3. Does this actually work for Public Folders that have subfolders with separate permissions? We would need each subfolder within the one Public Folder Mailbox to go to its own shared mailbox. Can this do that?

  4. I followed the guide and migrated our public folders to the shared inbox but our shared inbox is not accessible. We’ve shared permissions on the shared mailbox to IT staff, but when we look for it when trying to “add a shared mailbox” or “Open another mailbox” the name of our shared folder isn’t there. We tried converting it to a regular mailbox just to see if that would work, but it didn’t show up then either.

    • Have you started with creating a shared mailbox on the target Microsoft 365 tenant? As soon as you create such a group and add members to it, those members should be able to access the mailbox without any problems.

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