Is it possible to send emails created in Marketing Cloud Content Builder through the API? I don't mind whether it is SOAP or REST.
I'd like the data source to be a filter on a Data Extension.
When defining the ETEmail in the ETEmailSendDefinition you have to specify the 'CustomerKey' and not the ID.
It appears that if you want to send a 'Classic' email the ID works, however if you're trying to send a 'Content Builder' email you need to specify the 'CustomerKey'.