How to troubleshoot the quota exceeded issue with public folder migration?

Issue:

While migrating to Office 365 or Exchange public folders, you might come across the following error message.

Mailbox has exceeded maximum mailbox size.

or

An internal server error occurred. Try again later.

Resolution

How to resolve the issue 'target public folder mailbox quota is exceeded'?

Whenever the maximum size for your target primary public folder mailbox is reached, it will prompt the above error messages.

To resolve this issue, you must wait up to two weeks for the Office 365 AutoSplit feature to activate. Automatic splitting will generate a secondary mailbox for public folders and transfer some data from the primary mailbox to the secondary mailbox.

Note: When the aforementioned Public folder size limit is reached, it is not possible to transfer any new data to the mail-enabled Public folders. Other options that you can manually create Public folder mailboxes or contact Microsoft support to create before the migration process.

However, you cannot speed up the auto-split feature because it is set to run by default when the Public folder mailbox quota is reached.

After the auto-split is complete, repeat the migration with EdbMails. The incremental migration feature in EdbMails ensures that only new and updated items are migrated to the same public folder on subsequent migrations.

Note: To avoid problems with the auto-split function, use the organization's default storage quota as shown.

How to resolve the issue ‘target public folder quota is exceeded’?

The above error message may appear if the target's public folder quota does not match the source's, or if the source's quota is greater than the target's.

To fix this, change the quota settings in the target public folder to match the source. The steps for changing the public folder quota are as follows.

1. Open Windows PowerShell and connect to your target Office 365 tenant, Run the following command to check the existing public folder quota on the target.
   
   

   Get-OrganizationConfig | fl *DefaultPublicFolder*

2. The public folder quota in Office 365 is set to 2GB by default, and the IssueWarningQuota specifies the size of the Public folder at which a warning will be displayed.
    
3. Run the following commands to increase the ProhibitPostQuota and IssueWarningQuota to 50 GB and 40 GB respectively.
   
   

   Set-OrganizationConfig -DefaultPublicFolderProhibitPostQuota 50GB
   Set-OrganizationConfig -DefaultPublicFolderIssueWarningQuota 40GB

4. The changes take about an hour to propagate, after which you can resume the migration with EdbMails.