We are merging 2x companies @abc.com and @xyz.com. The networks are not interconnected at this stage. We want to achieve all staff seeing one single GAL and be able to book meetings between the 2x office.
Both companies plan to migrate to O365 as separate tenants. Does O365 federation allow us to achieve what I want (i.e. combined GAL)?
Before moving to O365, can forming inter-forest trust between the 2x active directory allow us to have a combined GAL?
Any suggestion will be greatly appreciated!
For on premises Exchange servers, you can use FIM 2010 or MIM 2016 on-premises to sync users (via GALSync) between two Exchange organizations. The users in one organization appear as foreign users/contacts in the other organization.
For two Office 365 tenants, we cannot do GALsync , but we can share calendars with another Office 365 organization. https://docs.microsoft.com/en-us/office365/enterprise/office-365-inter-tenant-collaboration Sharing in Exchange Online Organization relationships in Exchange Online Create an organization relationship in Exchange Online Modify and organization relationship in Exchange Online Remove an organization relationship in Exchange Online Share calendars with external users
There are many users report this issue/feature in Office 365 uservoice: https://office365.uservoice.com/forums/273493-office-365-admin/suggestions/10087845-gal-federation-between-different-o365-tenants