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In Microsoft Office 365 Dedicated/ITAR, you experience the following issues:

  • You receive a warning message in Microsoft Outlook that your mailbox is over the size limit.

  • You can't send or receive new email messages.

  • Your mailbox is not set to the appropriate size limit based on your plan type.


This issue occurs if one or more of the following conditions are true:

  • The extension attribute on the mailbox object is configured incorrectly.

  • Your mailbox is over the size limit, and a new mailbox type is authorized because your work is affected.

  • The quota management program isn't working as expected.


Mailbox quotas are generally applied to users according to the default values of the quotas on their Microsoft Exchange mailbox server databases. Mailbox quotas can be temporarily overridden at the mailbox level, as necessary.

These mailbox quota levels are managed by using the extension attributes in Active Directory Domain Services (AD DS). For more information, see Mailbox quotas in O365 Dedicated/ITAR.

The values typically resemble the following:


Note These values should include the semicolon.

The task by which quotas are applied in the managed environment runs one time per day. A quota that is applied by updating a user’s extension attribute may take up to 24 hours to apply. If the values are set incorrectly, or if they are left blank for any mailboxes, the mailbox quotas will remain unchanged.

If a user needs an immediate quota level increase, follow these steps:

  1. Set the appropriate value on the extension attribute.

  2. Contact Microsoft Online Services Support to request that the user’s quota be increased immediately.

    Note The request may take up to two hours to be completed. The user’s service will be affected during that time.

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