Yes, cross-tenant authentication for Exchange Online can be used to give users from one tenant access to Exchange Online resources in another tenant. This can be done by configuring a trust between the two tenants, which allows users from one tenant to be
authenticated by the other tenant's Active Directory. Once the trust is established, you can then use Exchange Online remote sharing features to give users from one tenant access to the other tenant's Exchange resources, such as mailboxes and calendar items.
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