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Configuring disk quotas for the POP3 service

Updated: January 21, 2005

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Configuring disk quotas for the POP3 service


  • You can configure disk quotas only on NTFS file system partitions.

You can use disk quotas to control and limit the amount of disk space individual mailboxes on the mail server can use. This ensures that individual mailboxes, and the mail store in general, do not use excessive or unanticipated amounts of disk space and adversely affect the performance of the server where the POP3 service is running.

For example, if the mail server suddenly receives a large volume of unsolicited e-mail, the mail store expands rapidly and might use all of the available disk space on the hard disk. If you implement quotas, the mail store only expands to the quota limit that you specified. As a result, no more mail is accepted by the server, and the rest of the server still functions normally.

If you are using Active Directory integrated authentication or local Windows accounts authentication, the e-mail delivered to a POP3 service mailbox will have file ownership assigned to the mailbox user by default. A quota file is created in the mailbox directory that contains the security identifier (SID) of the user account associated with the mailbox. File ownership is then assigned to the user account that corresponds to the SID contained in the quota file. The SID is also used by the NTFS file system disk quota system to enforce the quota limits specified on the user account matching the SID. All e-mail transferred to the mailbox's mail store directory is marked with the SID contained in the quota file; this marks the e-mail so it can be monitored by the quota system.

For more information, see Disk Quotas.

createquotafile command

If you are using encrypted password file authentication, there is no valid user account for the mailbox that the quota system can use. You can use the createquotafile /user command, however, to manually associate a given mailbox with a valid user account that is configured to have a disk quota. This association is for disk quota purposes only and is separate from mailbox authentication. If you are using Active Directory integrated authentication or local Windows accounts authentication, a quota file is created by default when you create a mailbox.

For more information about the createquotafile command, see Create a quota file.

Configuring domain disk quotas

Although quotas are designed to be implemented on a per-mailbox basis, you can create a domain-wide disk quota.

To create a disk quota for a domain, you must create a new mailbox and user account with an associated quota. The quota file for the new mailbox functions as a template that you can then copy into all of the other mailbox directories in the domain to create a domain-wide quota policy.

The following table describes the steps for creating a domain disk quota.


Step Reference

Create a new mailbox and user account. When you create the new mailbox, you must also create an associated user account for the mailbox. This account will be used to create a domain-wide quota. Other accounts in the domain can be configured to reference this account and its associated quota. All accounts associated with this account will have their disk usage aggregated under a single quota limit, which will create a domain-wide quota limit.

Create a mailbox

Enable disk quotas for the partition on which the mail store is configured.

Enable disk quotas

Create a quota to be used as the domain quota and assign it to the domain quota account.

Add new quota entries

Do one of the following:

  • Copy the quota file from the mail store directory of the domain account to the corresponding mail store directory of all the mailboxes in the domain.

  • Or, using the winpop createquotafile command and the /user: switch, associate one or more accounts in the domain with the domain account and its quota. For more information on the createquotafile command, see Create a quota file.



  • When a mailbox quota is exceeded, the user is not notified. E-mail intended for the user is not accepted, and a Non-Delivery Report (NDR), a notice that the e-mail was not delivered to the recipient, is returned to the sender.

  • Be sure that users configure their e-mail client to delete from the server any e-mail that has been successfully retrieved. If users leave successfully retrieved e-mail on the server, they can quickly exceed their quota. Users are likely to be unaware of the disk usage and impact of old e-mail stored on the server.

  • You cannot set quota limits on the accounts of Administrators or members of the Administrators group.

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