Cross Tenant Sync for GalSync?
Microsoft Entra ID’s Cross Tenant Sync can sync users from one tenant to another. They will sync as External Members or External Guests. In Exchange Admin they will show as MailUsers. Just be sure that showInAddressList is synced to be true or better yet carries over the showInAddressList from your source tenant. GalSync done! Yeah! Wait a minute! What about Groups? What about contacts? What about internal guests? NO! They are not supported