AAD Cross-Tenant Access Public Preview

The AAD team has put in a new public preview for cross-tenant access settings for external collaboration.  With this new feature, you have the ability to trust security claims from external AAD organizations.  A good example is, if an external user from a partner organization has already completed a MFA claim in their tenant, your tenant will trust that claim and allow the user to have access to approved resources in your tenant without requiring the external user to perform an additional MFA check within your tenant.  

Reference: https://techcommunity.microsoft.com/t5/azure-active-directory-identity/collaborate-more-securely-with-new-cross-tenant-access-settings/ba-p/2147077