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Create a Mailbox or Shared Mailbox in a Hybrid Exchange Environment

Create a Mailbox or Shared Mailbox in a Hybrid Exchange Environment

In a classic Exchange hybrid environment where on-premises Active Directory is the source of authority for recipient attributes, create and manage the recipient with supported Exchange tools rather than manually editing a collection of directory attributes.

User mailbox destined for Exchange Online

Create or identify the on-premises AD user, then use the on-premises Exchange Management Shell to enable the remote mailbox. Example:

Enable-RemoteMailbox -Identity "Alex Smith" \
  -RemoteRoutingAddress [email protected]

Shared mailbox

For a new remote shared mailbox, use the shared-mailbox option supported by your Exchange build, then allow Microsoft Entra Connect/Cloud Sync to synchronise the object. Verify the recipient in both on-premises Exchange and Exchange Online before assigning permissions.

Validation

  • Confirm primary SMTP and proxy addresses.
  • Confirm the remote routing address uses your tenant routing domain.
  • Wait for directory synchronisation and provisioning rather than creating a duplicate cloud-only object.
  • Test internal and external mail flow and then assign Full Access/Send As only to the required users.

Note: hybrid designs vary. If your organisation has moved recipient management to cloud-only tools, follow that documented operating model instead of mixing methods.