EX 10 to Ex 16 Migration - legacy Public Folder to Modern Public Folder ?

BR0KK 641 Reputation points

Hi there its me again;

....with some questions about legacy PF migration to the shiny new modern PF mailbox...

The System i'm currently migrating is based on a SBS 2011 Server with Ex 10 enabled.
I'm following a scenario for migration from Ex 10 to Ex 16.

All User Mailboxes have been moved from the Ex 10 to the Ex 16 already. Access to those mailboxes and sending recieving works internaly and externaly.

Tha paricular customer is a heavy Public Folder User .... they dump everything in there and so the PF database is currently at arroud 167 GB in size (1 Database with many folders and subfolders containing things only god knows about)...

There is a Proxy Mailbox in place so that all the Outlook clients (2016/19) can still access this PF - It also works fine

Now im at the stage where im supposed to move said legacy PF to the new server... And thats where my problems lie...

I read online that the new modern PF size is limmited (or lets better say only supported to) 100GB in size?

My leagacy PF is 167 GB in size ?

In my tests (i restored a full backup of the SBS 2011) the migration always works but who knows ....

So my question is :

What is MS way to deal with leagacy PF with sizes bigger than 20 GB?

What am i supposed to do?

thank you

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Lucas Liu-MSFT 6,076 Reputation points

    Hi @BR0KK ,
    For your first question:

    1. When your public folder mailbox has enough space, but if your single public folder exceeds the quota limit, you will no longer be able to store items in the public folder, and sending emails to the public folder will fail.
    2. If you want to continue use this public folder, you could move the items to another public folder when the storage quota reaches the value of "IssueWarningQuota". Another way is to change the name of the Public Folder that you continue to use and disable the mail function. Create a new Public Folder and name it the name of the Public Folder you want to continue to use and enable the mail function. To ensure that it can be used successfully in the actual production environment, please send a test email to check whether the new Public Folder can be successfully received.
      The screenshot below is a test that sends emails or moves items to a full public folder.

    For your second question:

    1. If you set the value of warning at 49GB, when the public folder mailbox storage reaches to 49GB, you will receive a reminder that the storage quota of public folder mailbox has used 49GB. At this time, you can set the storage quota of the Public folder mailbox to 100G, but as mentioned above, even if your public folder mailbox has a storage quota of 100G, it is recommended to set the warning value to a smaller value instead of 99GB, so that you will be enough time to move the project.
    2. Because in Exchange2016, the contents of the public folder are stored in the Public folder mailbox. If the public folder mailbox quota is used up, the public folder in it will no longer be able to receive mail or move items to it. Otherwise you will receive the error in the screenshot above. According to my test results, the storage quota of the public folder mailbox can exceed 100GB, but Microsoft does not officially support this, so when your public folder mailbox quota is about to be used up, it is recommended that you transfer some of the items or create a new public folder mailbox


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5 additional answers

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  1. Andy David - MVP 110.4K Reputation points Microsoft MVP

    The maximum supported Public Folder mailbox size is 100GB, not the folder itself. You can multiple folders in a public folder mailbox.
    If your folders exceed 100GB total, then you have multiple public folders mailboxes to handle it.

    The maximum supported folder size is 10GB

    When you migrate to modern public folders, the scripts are used to help spread the folders across the new public folder mailboxes


  2. BR0KK 641 Reputation points

    OK got a bit further down the rabbit hole....

    The value uf 9 GB doesn't work because the folder "info" is bigger than 33 GB in total without subfulders and the likes

    It has mails in there from 2015 which i can not delete becuse of a 10 year retention policy for business mails

    If i issue the command above with, lets say 36 GB in byte the script creates a new *.csv with 6 mailboxes (total)

    Yes i know .... ARCHIVING or deleting would be the right choice but .... :/

    And why should i use only 10 GB for the PF mailbox size ? I thought 100 GB was supported?

    Or how do i limit the size of one folder?

    Is each folder only supposed to be 10 GB?
    Is ist 10 GB in total (inkl. subfolders)?

    What about the customer ... they shurely can not see the size of their folders and frankly they wouldn't care either because it just has to work. Are they expected to look through all folders and check for the current size ?
    Are there warings in place ?

    And if i run with the 6 mailboxes, what happens if those run out of space?
    Do i need to go in there manually and create a new PF mailbox?
    Does exchange handle that if the pf mailbox runs out of space?


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  3. BR0KK 641 Reputation points

    Here is an example of what i get when i run the FolderToSizeMapGenerator: ( 36 GB Split into 6 Databases)

    "\IPM_SUBTREE\Info\1 Lxxxxx","Mailbox2"
    "\IPM_SUBTREE\Info\1 Lxxxxx\2 Hxxxx","Mailbox3"
    "\IPM_SUBTREE\Info\Alxxxxx\200x - 201x","Mailbox5"
    "\IPM_SUBTREE\Info\Alxxxxx\201x - 201x","Mailbox5"
    "\IPM_SUBTREE\Info\Alxxxxx\201x - 201x","Mailbox6"

    Here is what i get when i issue 100 GB:


    How is this read ?

    Lets assume i do the 100 GB one....

    Everything from root to "\IPM_SUBTREE\ALxxxx" is stored in the first mailbox
    Everything else in the second mailbox

    What then?

    Is the creation of those databases a manual task? So do i need to go into the EX 16 and issue this command 2x times:

    New-Mailbox -PublicFolder Mailbox1 -HoldForMigration:$true

    Or will this be taken care of with this command:

    New-MigrationBatch -Name PFMigration -SourcePublicFolderDatabase (Get-PublicFolderDatabase -Server EXCHANGESRV) -CSVData (Get-Content \\exchnageservername\C$\PFMigration\FolderToMailBoxMap.csv -Encoding Byte) -NotificationEmails administrator@.... 

    What about the concurrent connections .... What value am i supposed to use there since i only have 25 Users...

    Thank You again :)

  4. Lucas Liu-MSFT 6,076 Reputation points

    Hi @BR0KK ,
    1.According to my research, for public folder mailbox, the maximum supported size is 100G. Although it can exceed 100G in practice, unexpected errors may occur in subsequent practical applications, Microsoft does not officially support this. The maximum supported size for a single public folder is 10G. You could run the following command to set the quota of public folder, the default value of this attribute is unlimited. But it should be noted that because the quota of the public folder cannot exceed the quota of the public folder mailbox, first we need to run the following second command line so that we can define the quota of the public folder mailbox, and then run the following third command line to change public Quota for folder mailbox.

    Set-OrganizationConfig -DefaultPublicFolderIssueWarningQuota -DefaultPublicFolderProhibitPostQuota   
    Set-Mailbox -PublicFolder PublicFolder2 -UseDatabaseQuotaDefaults $false  
    Set-Mailbox -PublicFolder PublicFolder2 -ProhibitSendReceiveQuota <> -ProhibitSendQuota <>  

    2.For migrating public folders from Exchange 2010 to Exchange 2016, the batch migration method is the only supported method for migrating legacy public folders to Exchange Server. But please note that your Exchange 2010 version needs to be Exchange 2010 SP3 RU8 or later.
    For more information you could refer to:Use batch migration to migrate Exchange 2010 public folders to Exchange 2016

    3.For the .CSV files you mentioned, first you need to run the following first command line on Exchange 2010 to execute the Export-PublicFolderStatistics.ps1 script to create the folder name-to-folder size mapping file. Then run the following Two command lines to execute the PublicFolderToMailboxMapGenerator.ps1 script to create the public folder-to-mailbox mapping file. This file is used to calculate the correct number of public folder mailboxes on the Exchange 2016 server. The parameter Maximum mailbox size in bytes equals The maximum size you want to set for the new public folder mailboxes. As mentioned above, the maximum supported size is 100G, but when specifying this setting, be sure to allow for expansion so the public folder mailbox has room to grow.

    .\Export-PublicFolderStatistics.ps1 <Folder to size map path> <FQDN of source server>  
    .\PublicFolderToMailboxMapGenerator.ps1 <Maximum mailbox size in bytes> <Folder to size map path> <Folder to mailbox map path>  

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