Applies to: Exchange Server 2016

This cmdlet is available only in on-premises Exchange Server 2016.

Use the New-X400AuthoritativeDomain cmdlet to create and specify the X.400 authoritative domain for the organization. The X.400 authoritative domain defines the standard fields for the namespace appended to the recipient identity for all mailboxes assigned an X.400 address.

New-X400AuthoritativeDomain -Name <String> -X400DomainName <X400Domain> [-Confirm [<SwitchParameter>]] [-DomainController <Fqdn>] [-WhatIf [<SwitchParameter>]] [-X400ExternalRelay <$true | $false>]

This example creates the X.400 authoritative domain Sales in the private domain Contoso, which is under the administrative domain Fabrikam.

New-X400AuthoritativeDomain -Name Sales -X400DomainName "C=US;A=Fabrikam;P=Contoso;O=Sales"

This example creates an external relay domain for the X.400 namespace Europe organizational unit (OU) under the Sales organization in the private domain Contoso, which is under the administrative domain Fabrikam.

New-X400AuthoritativeDomain -Name "Sales Europe" -X400DomainName "C=US;A=Fabrikam;P=Contoso;O=Sales;OU1=Europe" -X400ExternalRelay: $true

X.400 domain names can only include the following ASCII characters:

  • A to Z

  • a to z

  • 0-9

  • These punctuation and special characters: (space) ' () + , - . / : = ?

You can use the following X.400 attributes (one each per address):

  • Name   country   Abbreviation   C   Maximum character length   2

  • Name   administrative domain   Abbreviation   A   Maximum character length   16

  • Name   private domain   Abbreviation   P   Maximum character length   16

  • Name   organization name   Abbreviation   O   Maximum character length   64

  • Name   organizational unit name   Abbreviation   Ou1-4   Maximum character length   32

You need to be assigned permissions before you can run this cmdlet. Although all parameters for this cmdlet are listed in this topic, you may not have access to some parameters if they're not included in the permissions assigned to you. To see what permissions you need, see the "X.400 domains" entry in the Mail flow permissions topic.


Parameter Required Type Description




The Name parameter specifies a unique name for an X.400 authoritative domain object. When you specify a name that includes spaces, you must enclose the name in quotation marks ("), for example, "Display Name". The Name parameter can't exceed 64 characters.




The X400DomainName parameter specifies the X.400 namespace, which can only include the X.400 organizational components. Specifically, only the following attribute types are supported:

  • Label (Abbreviation)

  • C (Country)

  • A (ADMD)

  • P (PRMD)

  • O (Organization)

  • OU1 (Organization unit 1)

  • OU2 (Organization unit 2)

  • OU3 (Organization unit 3)

  • OU4 (Organization unit 4)

The address attributes must be separated by semicolons, and the address must be enclosed in quotation marks ("), for example,





The Confirm switch specifies whether to show or hide the confirmation prompt. How this switch affects the cmdlet depends on if the cmdlet requires confirmation before proceeding.

  • Destructive cmdlets (for example, Remove-* cmdlets) have a built-in pause that forces you to acknowledge the command before proceeding. For these cmdlets, you can skip the confirmation prompt by using this exact syntax: -Confirm:$false.

  • Most other cmdlets (for example, New-* and Set-* cmdlets) don't have a built-in pause. For these cmdlets, specifying the Confirm switch without a value introduces a pause that forces you acknowledge the command before proceeding.




The DomainController parameter specifies the domain controller that's used by this cmdlet to read data from or write data to Active Directory. You identify the domain controller by its fully qualified domain name (FQDN). For example,

The DomainController parameter isn't supported on Edge Transport servers. An Edge Transport server uses the local instance of Active Directory Lightweight Directory Services (AD LDS) to read and write data.




The WhatIf switch simulates the actions of the command. You can use this switch to view the changes that would occur without actually applying those changes. You don't need to specify a value with this switch.




The X400ExternalRelay parameter specifies this authoritative domain as an external relay domain. If you set the X400ExternalRelay parameter to $true, Microsoft Exchange routes email to the external address and doesn't treat resolution failures to this subdomain as an error.

To see the input types that this cmdlet accepts, see Cmdlet Input and Output Types. If the Input Type field for a cmdlet is blank, the cmdlet doesn’t accept input data.

To see the return types, which are also known as output types, that this cmdlet accepts, see Cmdlet Input and Output Types. If the Output Type field is blank, the cmdlet doesn’t return data.