A matching connector cannot be found to route the external recipient

When I wanted to send an e-mail from my exchange mailbox to an external e-mail address, the message wasn't send.
I tracked the message in the Queue Viewer and it couldn't be sent because of this: "A matching connector cannot be found to route the external recipient".

To be able to send messages to external domains you have to create a send connector for domain "*". You can do this in the Organization Hub Transport Configuration: