The Active Directory Migration Tool allows you to migrate trust relationships from one domain to another domain. A trust relationship connects two or more domains and allows users in one domain to access resources in another domain.
Groups can contain members from trusted domains. To migrate groups with members from trusted domains, you should establish the same trust relationships in the target domain as exist in the source domain. If the Active Directory Migration Tool cannot identify a member account in the target domain, the tool does not add the member to the group.
The Trust Migration Wizard resolves this issue. The Trust Migration Wizard compares the trust relationships in the source domain to the trust relationships in the target domain. The Trust Migration Wizard establishes in the target domain any trust relationships that exist in the source domain but not in the target domain. This wizard does not affect any trusts that exist in the target domain but not in the source domain.