Shared SMTP domain between 2 hybrid Exchange environments

31 Mar

Initial situation

A shared SMTP domain between two hybrid Exchange environments, where no mailboxes are in the Office 365 tenant part.

The shared SMTP domain is @bigCompany.com

Company A mail-enabled objects (users and groups) has an addional smtp address @companyA.com

Company B mail-enabled objects (users and groups) has an addional smtp address @companyB.com


GALsync is used to synchronize the GAL between the two on-premise Exchange environments.

Company A:       The import police for Company B objects has the rule:   Use @companyB.com as targetAddress.

Company B:       The import police for Company A objects has the rule:   Use @companyA.com as targetAddress.

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Requirement

The Office 365 tenant also uses the shared SMTP address @BigCompany.com
and has an additional the smtp address @BigCompany.onmicrosoft.com

Some mailboxes of Company A users should be migrated to the Office 365 tenant part of the hybrid Exchange environment.

Some mailboxes of Company B users should be migrated to the Office 365 tenant part of the hybrid Exchange environment.

Company A: All imported contacts of company B, which have a cloud-migrated mailbox user needs the targetAddress of the Office 365 tenant @BigCompany.onmicrosoft.com instead of the old targetAddress @companyB.com

Company B: All imported contacts of company A, which have a cloud-migrated mailbox user needs the targetAddress of the Office 365 tenant @BigCompany.onmicrosoft.com instead of the old targetAddress @companyA.com


Solution proposal

This solution does not include specific aspects of the environment configuration, for example, but not limited to:

  • the exact configuration of the Microsoft Azure Active Directory Connect Tool
  • existing objects in the Office 365 tenant

Migrating mailboxes of Company A Users to Office 365

Company A:
All Company A objects, which mailboxes are migrated to Office 365, should be excluded from the existing export policy.
A second export policy should only export Company A objects, which have their mailbox in the Office 365 tenant.

The migrated mailbox users need the unique smtp address @BigCompany.onmicrosoft.com as additional smtp address in the proxyAddresses in the on-premise Active Directory user objects.

Company B:
The existing import policy, which imports mail-enabled objects from Company A as contacts, should only import the data file of the existing policy.
The import OU of the existing import policy should only contain imported contacts, which have source objects with on-premise mailboxes.

The existing imported contacts, which have source objects with cloud mailboxes, should be moved to an additional import OU for contacts of migrated mailboxes.
A second import policy updates the import OU for contacts of migrated mailboxes.
The second import police has the rule:  Use @BigCompany.onmicrosoft.com as targetAddress.

Note: This must happen before the next GALsync synchronization run starts, otherwise some contacts will be deleted. The general setting “Only mark to delete” should prevent that from happening.


Migrating mailboxes of Company B Users to Office 365

Company B:
All Company B objects, which mailboxes are migrated to Office 365, should be excluded from the existing export policy.
A second export policy should only export Company B objects, which have their mailbox in the Office 365 tenant.

The migrated mailbox users need the unique smtp address @BigCompany.onmicrosoft.com as additional smtp address in the proxyAddresses in the on-premise Active Directory user objects.

Company A:
The existing import policy, which imports mail-enabled objects from Company B as contacts, should only import the data file of the existing policy.
The import OU of the existing import policy should only contain imported contacts, which have source objects with on-premise mailboxes.

The existing imported contacts, which have source objects with cloud mailboxes, should be moved to an additional import OU for contacts of migrated mailboxes.
A second import policy updates the import OU for contacts of migrated mailboxes.
The second import police has the rule:  Use @BigCompany.onmicrosoft.com as targetAddress.

Note: This must happen before the next GALsync synchronization run starts, otherwise some contacts will be deleted. The general setting “Only mark to delete” should prevent that from happening.

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