"554 5.2.2 mailbox full" when sending emails to a mail-enabled public folder

Symptoms

A non-delivery report (NDR) is returned with error code 554 5.2.2 when sending emails to a mail-enabled public folder:

The recipient's mailbox is full and can't accept messages now. Please try resending this message later or contact the recipient directly.

Diagnostic information for administrators
Remote Server returned '554 5.2.2 mailbox full;
STOREDRV.Deliver.Exception:QuotaExceededException.MapiExceptionQuotaExceeded'

Cause

This issue occurs when any of these conditions is met:

• The organization's default public folder post quota (DefaultPublicFolderProhibitPostQuota) has been reached.
• The individual public folder post quota (PublicFolderProhibitPostQuota) has been reached.
• The Content Public Folder mailbox hosting the mail-enabled public folder has reached its quota.

Resolution

Here's how to identify which quota has been reached and take corrective steps:

Step 1: Check individual public folder quota

1. Connect to Exchange Online PowerShell.

2. Check the value of TotalItemSize for the affected mail-enabled public folder:

   Get-PublicFolderStatistics \pfname | FL TotalItemSize
   

3. Check if the value of TotalItemSize has reached or exceeded the value of ProhibitPostQuota.

   Get-PublicFolder \pfname | FL *quota*
   

   If that's the case, increase the ProhibitPostQuota value of that mail-enabled public folder or set it to Unlimited.

   Note

   If the default value of prohibitpostquota is set to Unlimited, the value that was configured for DefaultPublicFolderProhibitPostQuota at the organization level applies. If the PublicFolderProhibitPostQuota value has been configured on the public folder, this value will take precedence over the value set at the organization level.

   For more information, read Understanding modern public folder quotas.

4. Check if the value of TotalItemSize has exceeded the value of DefaultPublicFolderProhibitPostQuota:

   Get-OrganizationConfig | FL *quota*
   

   A TotalItemSize larger than DefaultPublicFolderProhibitPostQuota prevents mail-enabled public folders from accepting new emails.

Here are two ways to resolve this issue:

1. Increase the ProhibitPostQuota of the public folder at the user level if there are only a few affected public folders.

   Set-PublicFolder \pfname -ProhibitPostQuota 5GB -IssueWarningQuota 4GB
   

2. Increase the DefaultPublicFolderProhibitPostQuota for all public folders at the organization level.

   Set-OrganizationConfig -DefaultPublicFolderProhibitPostQuota 5GB -DefaultPublicFolderIssueWarningQuota 4GB
   

If this quota hasn't been exceeded, proceed to the next step.

Step 2: Check the content public folder mailbox quota

If the public folder hasn't exceeded the individual or organizational quota as shown in Step 1, check if the public folder mailbox hosting the public folder content has exceeded its quota.

1. Connect to Exchange Online PowerShell.

2. Find the content public folder mailbox's name for the mail-enabled public folder:

   Get-PublicFolder \pfname |FL name, *content*
   

3. Check the value of TotalItemSize for the content public folder mailbox:

   Get-MailboxStatistics pfmbx | FL TotalItemSize
   

4. Check if the value of TotalItemSize has exceeded the value of ProhibitSendRecieveQuota:

   Get-Mailbox -PublicFolder pfmbx | FL *quota*
   

When a quota is reached, the auto-split process should create a new public folder mailbox and move some of that content to a newly created auto-split mailbox. To check that, run this command:

Get-PublicFolder \pfname |Ft name, *content*

For more information, read the following Blog articles:

• How Exchange Online automatically cares for your public folder mailboxes (via AutoSplit)
• Public Folders and Exchange Online

If the auto-split process failed to create a new mailbox, please submit a support request to Microsoft Support for further assistance.