You are building an industrial IoT solution where, using several IoT hubs, you collect telemetry data from a number of field sensors. The final destination of the data is Azure Cosmos DB and you need to establish a route to forward messages from your IoT hubs. In addition, each message needs to be stamped with the name of the IoT hub ($iothubname) which it originates from, to enable further classification. You decide to use IoT hub’s message routing. 
Does it help you to achieve your goal?

Answer options:

A.Yes
B.No

Correct Answer: B
Option A is incorrect because although, through the Custom endpoint feature, IoT hubs can be linked to several other Azure services as sinks for messages, Cosmos DB is not one of them, so it cannot be targeted directly. Messages can be routed to Storage Containers and then further to Cosmos DB, for example.
Option B is CORRECT because with IoT hub’s routing capability, you can forward incoming messages to other Azure services as Custom endpoints. CosmosDB is not among the available endpoints, therefore message routing cannot be used for this use case.
References: 

https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-endpoints#custom-endpoints
https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-messages-d2c#routing-endpoints