How can I send an email from my Exchange Server to Microsoft Exchange Online

Hi, 

I have a requirement to route secure SMTP messages through my On-Premise Exchange Server to Exchange Online. 

What is the best way to do this? 

The Server was setup with a Send Connector to Exchange Online but I am not entirely sure about the process. 

Will I need to create a receive connector for secure smtp and point the apps and devices to sent to it? 

Will I have to get them to use an account that exists in Exchange Online to authenticate? 

What is the best way to do this? 

Thanks