Single On-Premises Exchange to Multiple Office 365 Tenants – Part 2

This blog is a continuation to Part 1.

TechPoss Organization – On Premises Setup

TechPoss is a fictional organization which has 2 business entities Technically Possible and Hybrid Shell. IT infrastructure is currently managed by TechPoss central IT.

Network Diagram

Active Directory

TechPoss has a single active directory forest/domain techposs.internal and an On-premises Exchange Organization. Users and computers of the business entities Technically Possible and Hybrid Shell are located under dedicated OUs. UserPincipalName of the users are updated to match the email address of the users.

Domains technicallypossible.com and hybridshell.com are defined as UPN Suffixes in Active Directory Domains and Trusts.


TechnicallyPossible.com and HybridShell.com smtp domains are configured as accepted domains in the exchange organization.

Email Address Policies are targeted to OUs.

Email Address Lists are created for each department based on OUs.

Clients & SMTP

Exchange servers are published to internet through a load balancer. All client connections are available internally and externally using single namespace mail.technicallypossible.com. Autodiscover records are configured for both technicallypossible.com and hybridshell.com domains.

Inbound and Outbound traffic are routed through a third party email gateway solution. MX and SPF records configured towards the gateways.

Outlook Address Book Experience

Technically Possible Department users can select Hybrid Shell users from address book

Hybrid Shell Department users can select Technically Possible users from address book

Whats Next

TechPoss decided to move to Office 365. In the upcoming parts we will see the One-to-Many Hybrid and setting up Sync-GalToMutipleTenants tool for address book synchronization.

Part 1 – Continue Reading – Part 3

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