Need to share the exchange Global Address List (GAL) between two organizations in same group

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We have a single enterprise agreement with two tenants.  Both the organizations are under same group. One tenant is on hybrid exchange setup with O365 and on-premise exchange while the other tenant is on O365 alone. We need to share the exchange Global Address List (GAL) between each other organizations. Please advice the best method to achieve this requirement.

5 Replies

@udaraso My organization had a similar issue a few years ago and at the time there was no way to do within O365. So we wrote a PowerShell script to first bulk populate one tenant with contacts matching the info in the other tenants GAL, and then created a daily process to update, add new, and delete old entries in the other tenant. 

@IczerSigma215 Will you be able to share the PS script with me to give it a try?

I cannot as my company owns the code we create and I would need to put alot of time and effort to clean up internal references. It should be fairly simple to reproduce for anyone with PowerShell experience.

Sharing of global access lists (GALs) or moving user mailboxes between Exchange Online organizations in different Microsoft plans is not supported in federated sharing.

https://docs.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/s...

To me 3rd party is a better solution and multiple companies are offering it.