The following accepted domains '{0}' don't have an Outbound Connector to deliver mail to your On-premise mail servers. Make ...

The following accepted domains '{0}' don't have an Outbound Connector to deliver mail to your On-premise mail servers. Make sure that there's an Outbound Connector of the type OnPremises that matches every 'internal relay' accepted domain. The connector can either have the AllAcceptedDomains flag enabled or have a recipient domain that matches the accepted domain.