Sharing Global Address List
Currently it is not possible for different tenants to share the Global Address list.
But the function that Admin User can set GAL sharing with different tenants will be an effective feature for users.
This feedback is based on a customer voice from support SR.
Wiebe Niehof commented
We build a solution that not only allows GAL Federations between different Office365 Tenants, but even to companies that use Google GSuite contacts, Okta, OneLogin etc customers.
Completely pre-integrated with your current GAL. It automatically syncs between all those sources.
Check it out: https://www.federated.directory
In Microsoft AppSource:
In Microsoft Azure AD Marketplace:
I hope our solution helps you out!
I agree that it would be very effective