Connecting Single On-Premise AD to Multiple O365 Tenant


Please pardon me for posting this kind of question. I found some post with similar issues but my problem has something different that made me create another thread.




We have this existing client that has 7 separate O365 tenants. They decided to separate the tenants because of the 300 license limitation for Business Premium plans.

These tenants have different domains and different set of users. However, they are now requesting that all of the users from these 7 tenants will be able to see each other in the Global Address List.


I have read that this is not possible but I really need to know what are my options in this scenario.


Client has a single Active Directory on-premise that contains all the users from these 7 tenants. Also, they are NOT using Exchange On-premise.


Thanks in Advance

11 Replies

Hi @almarlibetario,


You can create contacts to in each tenant regarding the other users to have them on the GAL, you cannot sync the same object to different tenants.

AFAIK, your option here is to create contacts from other tenants for each tenant in question! There’s no GAL sync option that I’m aware of between tenants

Sorry didn’t see you there!

@Nuno Silva 


Yes, this is the first thought that came in my mind when this concern came in. However, maintaining 300 users in 7 tenants is not practical to do. Because if there is any change in one user, I have to change it across the 7 tenants.

Check out different 3 party tools for this!
I’ll msg you a link

Thanks @adam deltinger .


Is it safe to say that Microsoft's current technology does not support this kind of scenario? Do I really need to use a 3rd party system?


If you have synchronization with your AD with all of your tenant's with different AD Connect servers using different OUs, you can create a script to do that.

Hi @Nuno Silva ,


Thank you for your reply. I am not sure if this is possible but is it okay if you a share sample script for my reference?

best response confirmed by almarlibetario (Contributor)

I do not have a sample script, but the idea is you to centrally create a contacts in a OU and have a script to copy the contacts to another OU with adding something like company name to the end to be different in your active directory, then that OU is synced to their respective tenant.
Just an idea.

Thank you @Nuno Silva,


I will look into it and will provide the update how am I going to address the concern.


Your response is really helpful


@almarlibetarioone good solution I know about is

however am thinking out loud 7*1*250 (average users per tenant) = 1750 $/month