Mail-Enabled Public Folder and Public Folder Mailbox

Mail-Enabled Public Folder and Public Folder Mailbox

Mail enabled public folders and public folder mailboxes seem to be the same, but they are not. We will explore what each of these is, why they are different, and how this can help you manage or migrate your public folders.

What are mail enabled public folders?

A mail enabled public folder is exactly what it says, it is a folder that can receive e-mail. You can mail-enable any public folder. So, whether you mail-enable 10, 1,000, or even 10,000, each one will have its own unique e-mail address. For on-premise Exchange, a mail enabled public folder will use the public folder name to create an alias and your primary vanity domain to create the e-mail address. A public folder named \Commercial and the domain will create an e-mail address for the public folder For Exchange Online, it will use the tenant domain name by default instead of your vanity domain name, so it would be A public folder alias that matches another object in Exchange appends a number to it, such as

A mail enabled public folder can have multiple e-mail addresses. These e-mail addresses can have different aliases and vanity domains, making them very flexible. The only requirement is that the email address must remain unique.

There are two ways you can mail enable a public folder:

  • Exchange Admin Center
  • PowerShell

Exchange Admin Center

  1. Open the Exchange Admin Center

  2. Click on Public Folders on the left-hand side.

    Exchange Admin Center - Public Folders

  3. Click on Public Folders at the top of the main window.

    Exchange Admin Center - Public Folders Menu

  4. Click on the public folder you want to mail-enable. In this case, I picked the \Commercial folder. Under the Mail enabled column, it says No at this point.

    Mail-enable public folder

  5. Clicking the \Commercial folder name brings up a window on the right-hand side. Check the Mail enabled checkbox at the bottom, then click Save.

    Mail-enable public folder

  6. New mail enabled options appear in the public folder properties.

    Mail-enabled public folder options

  7. The Mail Properties tab allows you to change the Alias assigned and the option to hide the mail enabled public folder from the address list.

    Public Folder alias and hide address list

    Clicking on Edit general mail properties will give you the option to change the Alias, Display name, or both. Changing the Alias changes the default e-mail address assigned to the mail enabled public folder. The Display Name is how the name is displayed in an address list. None of these options will change the name of the public folder. These settings are a part of the mail enabled public folder active directory object, so they only reference the associated public folder.

    Alias and Display Name

  8. The Other tab gives you the option to modify or add e-mail addresses, assign group membership, set customer attributes, set e-mail forwarding, and set message size and delivery restrictions.

  9. The Delegation tab allows you to assign either Send As or Send on behalf permissions. Setting Send As means gives the user the option to send e-mail directly from the mail enabled public folder e-mail address. It will look like the e-mail was sent from Send on behalf is similar to Send As, but it will show the user that is sending the email and the mail enabled public folder e-mail address

    Send As and Send on Behalf for mail-enabled public folders


  1. Open either the on-premise Exchange Management Shell or a PowerShell session and connect to Exchange Online using the Exchange Online Management Shell.

  2. Use the Enable-MailPublicFolder command to mail-enable the public folder:

    Enable-MailPublicFolder “\Commercial”

  3. To make changes to the mail-enabled public folder, first, disable the E-Mail Address Policy on the mail-enabled public folder using the Set-MailPublicFolder command:

    Set-MailPublicFolder -Identity “\Commercial” -EmailAddressPolicyEnabled $False

  4. Multiple e-mail addresses can be added using the Set-MailPublicFolder command:

    Set-MailPublicFolder -Identity “\Commercial” -EmailAddresses @{add=””,””}

    Remove one or more e-mail addresses using the Set-MailPublicFolder command:

    Set-MailPublicFolder -Identity “\Commercial” -EmailAddresses @{remove=””}

  5. Send on Behalf is set using the Set-MailPublicFolder and the -GrantSendOnBehalfTo option.

  6. To set Send-As permissions, use the Add-RecipientPermission command.

Learn more about how ExchangeSavvy can help you with Public Folders!

What are Public Folder Mailboxes?

A public folder mailbox seems like it is a mailbox for public folders, which is true. However, these are not the same as mail-enabled public folders.

Public folder mailboxes serve two purposes, to store a portion of your public folders and to hold a copy of the public folder hierarchy. Public folders used the public folder database in Exchange 2010 and prior. Since Exchange 2013, including Exchange Online, a special type of mailbox called a public folder mailbox was added to store public folders under a mailbox database. This allowed public folders to fall under a database availability group (DAG) in Exchange for fail-over and high availability support. A public folder mailbox has a size limit, which is typically 100 GB in Exchange Online, but can be higher in Exchange on-premise (Microsoft will not support Public Folder Mailboxes over 100 GB on-premise). Exchange Online can handle up to 1,000 public folder mailboxes.

Public folder mailboxes also store a copy of the entire public folder hierarchy. The first public folder mailbox created is the primary public folder mailbox. This public folder mailbox contains the read/write copy of the public folder hierarchy while others are secondary. Any public folder mailbox created with the -IsExcludedFromServingHierarchy flag set to $false will hold a read-only copy of the public folder hierarchy. These secondary public folder mailboxes receive hierarchy updates from the primary public folder mailbox.

Users can see the public folder hierarchy by configuring their mailbox to point to a public folder mailbox. You can set the public folder mailbox to use with the -DefaultPublicFolderMailbox setting. Setting the -DefaultPublicFolderMailbox to nothing inherits a random public folder mailbox from the organizational configuration settings. The -EffectivePublicFolderMailbox setting will show the result of the -DefaultPublicFolderMailbox setting.

What is the difference between a mail-enabled public folder and a public folder mailbox?

These two terms are often confused with each other. Those with a very large public folder hierarchy and many thousands of mail-enabled public folders might think that they cannot migrate. They confuse mail-enabled public folders with public folder mailboxes. Below is a comparison between them:

A mail-enabled public folder:

  • Receive e-mail
  • Have one or more e-mail addresses
  • Assigned to a distribution group
  • Send mail from or on behalf
  • Any public folder can be mail-enabled

A public folder mailbox:

  • Has an e-mail address but cannot receive e-mail
  • Stores multiple public folders and their content
  • Maintains a copy of the complete public folder hierarchy
  • Assigned to a user mailbox for public folder access
  • Maximum of 1,000 public folder mailboxes per Exchange organization or Exchange Online tenant

Managing or Migrating Public Folders

Understanding the difference between mail-enabled public folders and public folder mailboxes helps with managing or migrating your public folders. A mail-enabled public folder is an easy way to file e-mails to a specific location, such as for managing projects. You can spread out your public folders to multiple public folder mailboxes. This can improve public folder performance.

Migrating public folders can be done for almost any public folder environment, no matter how many mail-enabled public folders exist. As long as you have less than 500,000 total public folders, you can migrate them.

Contact us to learn more about how ExchangeSavvy can help you with your public folder management and migration needs!

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