Users in a hybrid deployment can't access a shared mailbox that was created in Exchange Online
Content provided by Microsoft
Applies to: Exchange OnlineExchange Server 2016 Enterprise EditionExchange Server 2016 Standard EditionExchange Server 2013 EnterpriseExchange Server 2013 Standard EditionExchange Server 2010 EnterpriseExchange Server 2010 StandardMore
You have a hybrid deployment of on-premises Microsoft Exchange Server and Microsoft Exchange Online in Office 365.
You create a shared mailbox directly in Exchange Online.
You assign Full Access permissions to one or more users.
In this scenario, you experience one or more of the following issues:
Users can't open the shared mailbox in Outlook.
Users can't view free/busy information for the shared mailbox.
Users can't send mail to the shared mailbox.
These issues can occur when the shared mailbox is created by using the Exchange Online management tools. In this situation, the on-premises Exchange environment has no object to reference for the shared mailbox. Therefore, all queries for that SMTP address fail.
Create a remote mailbox in the on-premises environment, and then move the mailbox to Exchange Online. To do this, follow these steps:
Convert the shared mailbox to a regular mailbox by using the Exchange admin center in Exchange Online. To do this, follow these steps:
Open the Exchange admin center in Exchange Online.
Click recipients, and then click shared.
Select the shared mailbox, and then click Convert.
On the Warning page, select Yes to convert the shared mailbox.
Create an on-premises object for the cloud mailbox by using the New-RemoteMailbox cmdlet in the Exchange Management Shell.
Note This object must have the same name, alias, and user principal name (UPN) as the cloud mailbox.