Prepare mailboxes for cross-forest move requests

Mailbox moves and mailbox migrations in Exchange 2016 and Exchange 2019 from one forest to another require that you prepare the destination forest, which is made easier by Exchange tools and cmdlets. Exchange 2016 supports mailbox moves and migrations using the Exchange Management Shell, specifically the New-MoveRequest and New-MigrationBatch cmdlets. You can also move the mailbox in the Exchange admin center (EAC).

To move an Exchange mailbox from a source forest to the target Exchange 2016 or Exchange 2019 target forest, the target forest needs to contain a valid mail user (also known as a mail-enabled user) with a specified set of Active Directory attributes.

  • In Exchange 2016, you can move an Exchange 2010, Exchange 2013, or Exchange 2016 mailbox from a source Exchange forest to a target Exchange 2016 forest. If there's at least one Exchange 2016 Mailbox server in the target forest, the forest is considered an Exchange 2016 forest.

  • In Exchange 2019, you can move an Exchange 2013, Exchange 2016, or Exchange 2019 mailbox from a source Exchange forest to a target Exchange 2019 forest. If there's at least one Exchange 2019 Mailbox server in the target forest, the forest is considered an Exchange 2019 forest.

To prepare for the mailbox move, you need to create mail users (also known as mail-enabled users) with the required Active Directory attributes in the target forest. There are two recommended approaches for creating mail users with the necessary attributes:

  • If you deployed Identity Lifecycle Manager (ILM) for cross-forest global address list (GAL) synchronization, we recommend that you use Microsoft Identity Manager 2016 Service Pack 1. We've created sample code that you can use to learn how to customize ILM to synchronize the source mailbox user and target mail user.

    For more information, including how to download the sample code, see Prepare mailboxes for cross-forest moves using sample code.

  • If you created the target mail user using an Active Directory tool other than ILM or Microsoft Identity Integration Server (MIIS), use the Update-Recipient cmdlet with the Identity parameter to generate the LegacyExchangeDN attribute for the target mail user. We've created a sample PowerShell script that reads from and writes to Active Directory and calls the Update-Recipient cmdlet.

    For more information about using the sample script, see Prepare mailboxes for cross-forest moves using the Exchange Management Shell.

After creating the target mail user, you can then run the New-MoveRequest or the New-MigrationBatch cmdlets to move the mailbox to the target Exchange 2016 or Exchange 2019 forest.

For more information about remote move requests, see the following topics:

For more information about remote mailbox moves and remote legacy moves, see Move Mailboxes to Exchange 2016.

The remainder of this topic describes the mail user Active Directory attributes that are required for a mailbox move. These attributes are configured for you when you use either the code or the script to prepare for the mailbox move. However, you can manually copy these attributes using an Active Directory editor.

Active Directory user attributes required for a mailbox move

To support a remote mailbox move, the mail user object in the target Exchange forest must have the Active Directory attributes that are described in this section:

  • Mandatory attributes

  • Optional attributes

  • Linked attributes

  • Linked user attributes

  • Resource mailbox attributes

  • Additional attributes

Mandatory attributes

The following table lists the minimum set of attributes that need to be configured in ILM on the target mail user for the New-MoveRequest cmdlet to function correctly.

Mail user attributes

Active Directory attribute Action
displayName Copy the corresponding attribute of the source mailbox or generate a new value.
Mail Directly copy the corresponding attribute of the source mailbox.
mailNickname Copy the corresponding attribute of the source mailbox or generate a new value.
msExchArchiveGUID and msExchArchiveName Directly copy the corresponding attribute of the source mailbox.
msExchMailboxGUID Directly copy the corresponding attribute of the source mailbox.
msExchRecipientDisplayType -2147483642 decimal (equivalent to 0x80000006 hex).
msExchRecipientTypeDetails 128 decimal (0x80 hex).
msExchUserCulture Directly copy the corresponding attribute of the source mailbox.
msExchVersion 44220983382016 (decimal).
cn Copy the corresponding attribute of the source mailbox or generate a new value.
proxyAddresses Copy source mailbox's proxyAddresses attribute. Additionally, copy source mailbox's LegacyExchangeDN as an X500 address in the proxyAddresses attribute of the target mail user.
Note: The proxyAddresses of the source mailbox user must contain an SMTP address that matches the authoritative domain of the target forest. This allows the New-MoveRequest cmdlet to correctly select the targetAddress of the source mail-enabled user (converted from the source mailbox user after the mailbox move request is complete) to ensure that mail routing is still functional.
sAMAccountName Copy the corresponding attribute of the source mailbox or generate a new value.
Ensure that the value is unique within the target forest domain that the target mail user belongs to.
targetAddress Set to an SMTP address in the proxyAddresses attribute of the source mailbox.
This SMTP address must belong to the authoritative domain of the source forest.
userAccountControl Constant: 514 (equivalent to 0x202, ACCOUNTDISABLE | NORMAL_ACCOUNT).
userPrincipalName Copy the corresponding attribute of the source mailbox or generate a new value. Because the mail user is logon disabled, this userPrincipalName isn't used.

Optional attributes

The following attributes aren't required for the New-MoveRequest cmdlet to function correctly; however, synchronizing them provides a better end-to-end user experience after moving the mailbox. Because the GAL in the target forest displays this target mail user, you should set the following GAL-related attributes.

GAL-related attributes

Mail user's Active Directory attribute Action
c Directly copy the corresponding attribute of the source mailbox.
co Directly copy the corresponding attribute of the source mailbox.
countryCode Directly copy the corresponding attribute of the source mailbox.
company Directly copy the corresponding attribute of the source mailbox.
department Directly copy the corresponding attribute of the source mailbox.
facsimileTelephoneNumber Directly copy the corresponding attribute of the source mailbox.
givenName Directly copy the corresponding attribute of the source mailbox.
homePhone Directly copy the corresponding attribute of the source mailbox.
info Directly copy the corresponding attribute of the source mailbox.
initials Directly copy the corresponding attribute of the source mailbox.
l Directly copy the corresponding attribute of the source mailbox.
mobile Directly copy the corresponding attribute of the source mailbox.
msExchAssistantName Directly copy the corresponding attribute of the source mailbox.
msExchHideFromAddressLists Directly copy the corresponding attribute of the source mailbox.
otherHomePhone Directly copy the corresponding attribute of the source mailbox.
otherTelephone Directly copy the corresponding attribute of the source mailbox.
pager Directly copy the corresponding attribute of the source mailbox.
physicalDeliveryOfficeName Directly copy the corresponding attribute of the source mailbox.
postalCode Directly copy the corresponding attribute of the source mailbox.
sn Directly copy the corresponding attribute of the source mailbox.
st Directly copy the corresponding attribute of the source mailbox.
streetAddress Directly copy the corresponding attribute of the source mailbox.
telephoneAssistant Directly copy the corresponding attribute of the source mailbox.
telephoneNumber Directly copy the corresponding attribute of the source mailbox.
title Directly copy the corresponding attribute of the source mailbox.

Linked attributes

A linked attribute is an Active Directory attribute that references other Active Directory objects in the local forest. You can't directly copy the linked attribute values from a mailbox in the source forest to a mail user in the target forest. Instead, you do the following steps:

  1. Find the Active Directory objects in the source forest that the source mailbox attribute refers to.

  2. Find the corresponding Active Directory objects in the target forest.

  3. Set the target mail user's attribute to refer to the Active Directory objects in the target forest.

Linked attributes

Mail user's Active Directory attribute Action
altRecipient Correspond to the source mailbox's altRecipient attribute.
deliverAndRedirect Directly copy the corresponding attribute of the source mailbox. This attribute is a Boolean value that should be set along with altRecipient.
Manager (and its backlinks) Correspond to the source mailbox's manager attribute.
MemberOf (backlinks) This is the backlink of group member attribute.
publicDelegates (and its backlinks) Correspond to the source mailbox's publicDelegates attribute.

Linked user attributes

If you want to move a mailbox to an Exchange resource forest, the mailbox in the resource forest is considered a linked mailbox. In this scenario, you need to create a linked mail user in the (target) resource forest. To create a linked mail user, you need to set the attributes shown in the following table.

Linked mail user attributes

Active Directory attribute Action
msExchMasterAccountHistory Directly copy the corresponding attribute of the source mailbox.
msExchMasterAccountSid If the source mailbox has msExchMasterAccountSid, copy it. Otherwise, copy the source mailbox's objectSid.
msExchRecipientDisplayType Constant:-1073741818 decimal (equivalent to *unsigned* 0xC0000006).

Note

A linked mailbox can only be created if there's a forest trust between the source forest and target forest.

If the source object is disabled and the msExchMasterAccountSid attribute is set to self (resource mailbox, shared mailbox), don't stamp anything on the target user.

If the source object is disabled and the msExchMasterAccountSid attribute isn't set, the mailbox is invalid.

If the source object is enabled and the msExchMasterAccountSid attribute is set, the mailbox is invalid.

Resource mailbox attributes

If you want to move a resource mailbox to an Exchange forest, you need to set the attributes shown in the following table on the target mail user.

Resource mailbox attributes

Mail user's Active Directory attribute Action
msExchRecipientDisplayType If the source mailbox is a conference room: Constant: -2147481850 decimal (equivalent to *unsigned* 0x80000706).
If the source mailbox is an equipment mailbox: Constant: -2147481594 decimal (equivalent to *unsigned* 0x80000806).
msExchResourceCapacity Directly copy the corresponding attribute of the source mailbox.
msExchResourceDisplay Directly copy the corresponding attribute of the source mailbox.
msExchResourceMetaData Directly copy the corresponding attribute of the source mailbox.
msExchResourceSearchProperties Directly copy the corresponding attribute of the source mailbox.

Additional attributes

Resource mailbox attributes

Mail User's Active Directory attributes Description
comment Directly copy the corresponding attribute of the source mailbox.
deletedItemFlags Directly copy the corresponding attribute of the source mailbox.
delivContLength Directly copy the corresponding attribute of the source mailbox.
departmentNumber Directly copy the corresponding attribute of the source mailbox.
description Directly copy the corresponding attribute of the source mailbox.
division Directly copy the corresponding attribute of the source mailbox.
employeeID Directly copy the corresponding attribute of the source mailbox.
employeeNumber Directly copy the corresponding attribute of the source mailbox.
employeeType Directly copy the corresponding attribute of the source mailbox.
extensionAttribute1-15 Directly copy the corresponding attribute of the source mailbox.
homePostalAddress Directly copy the corresponding attribute of the source mailbox.
internationalISDNNumber Directly copy the corresponding attribute of the source mailbox.
ipPhone Directly copy the corresponding attribute of the source mailbox.
language Directly copy the corresponding attribute of the source mailbox.
lmPwdHistory Directly copy the corresponding attribute of the source mailbox.
localeID Directly copy the corresponding attribute of the source mailbox.
mAPIRecipient Directly copy the corresponding attribute of the source mailbox.
middleName Directly copy the corresponding attribute of the source mailbox.
msDS-PhoneticCompanyName Directly copy the corresponding attribute of the source mailbox.
msDS-PhoneticDepartment Directly copy the corresponding attribute of the source mailbox.
msDS-PhoneticDisplayName Directly copy the corresponding attribute of the source mailbox.
msDS-PhoneticFirstName Directly copy the corresponding attribute of the source mailbox.
msDS-PhoneticLastName Directly copy the corresponding attribute of the source mailbox.
msExchBlockedSendersHash Directly copy the corresponding attribute of the source mailbox.
msExchELCExpirySuspensionEnd Directly copy the corresponding attribute of the source mailbox.
msExchELCExpirySuspensionStart Directly copy the corresponding attribute of the source mailbox.
msExchELCMailboxFlags Directly copy the corresponding attribute of the source mailbox.
msExchExternalOOFOptions Directly copy the corresponding attribute of the source mailbox.
msExchMessageHygieneFlags Directly copy the corresponding attribute of the source mailbox.
msExchMessageHygieneSCLDeleteThreshold Directly copy the corresponding attribute of the source mailbox.
msExchMessageHygieneSCLJunkThreshold Directly copy the corresponding attribute of the source mailbox.
msExchMessageHygieneSCLQuarantineThreshold Directly copy the corresponding attribute of the source mailbox.
msExchMessageHygieneSCLRejectThreshold Directly copy the corresponding attribute of the source mailbox.
msExchMDBRulesQuota Directly copy the corresponding attribute of the source mailbox.
msExchPoliciesExcluded Directly copy the corresponding attribute of the source mailbox.
msExchSafeRecipientsHash Directly copy the corresponding attribute of the source mailbox.
msExchSafeSendersHash Directly copy the corresponding attribute of the source mailbox.
msExchUMSpokenName Directly copy the corresponding attribute of the source mailbox.
otherFacsimileTelephoneNumber Directly copy the corresponding attribute of the source mailbox.
otherIpPhone Directly copy the corresponding attribute of the source mailbox.
otherMobile Directly copy the corresponding attribute of the source mailbox.
otherPager Directly copy the corresponding attribute of the source mailbox.
preferredDeliveryMethod Directly copy the corresponding attribute of the source mailbox.
personalPager Directly copy the corresponding attribute of the source mailbox.
personalTitle Directly copy the corresponding attribute of the source mailbox.
photo Directly copy the corresponding attribute of the source mailbox.
pOPCharacterSet Directly copy the corresponding attribute of the source mailbox.
pOPContentFormat Directly copy the corresponding attribute of the source mailbox.
postalAddress Directly copy the corresponding attribute of the source mailbox.
postOfficeBox Directly copy the corresponding attribute of the source mailbox.
primaryInternationalISDNNumber Directly copy the corresponding attribute of the source mailbox.
primaryTelexNumber Directly copy the corresponding attribute of the source mailbox.
showInAdvancedViewOnly Directly copy the corresponding attribute of the source mailbox.
street Directly copy the corresponding attribute of the source mailbox.
terminalServer Directly copy the corresponding attribute of the source mailbox.
textEncodedORAddress Directly copy the corresponding attribute of the source mailbox.
thumbnailLogo Directly copy the corresponding attribute of the source mailbox.
thumbnailPhoto Directly copy the corresponding attribute of the source mailbox.
url Directly copy the corresponding attribute of the source mailbox.
userCert Directly copy the corresponding attribute of the source mailbox.
userCertificate Directly copy the corresponding attribute of the source mailbox.
userSMIMECertificate Directly copy the corresponding attribute of the source mailbox.
wWWHomePage Directly copy the corresponding attribute of the source mailbox.