If I want to use my own class as a job handler, where should I put it?

The docs mention the class SendEmail but nothing is said on where it should be.

Missed the fact that the classname should be namespaced: Queue::push('\YourName\PluginName\classes\SendEmail', ['message' => $message]);

I am facing the same problem. Wondering how to make:job by artisan or somewhere in the octobercms.

I found the solution now. You have to write your own class so that it could be used by the queue daemon.

Queue::push('\Skygdi\SendEmail\Jobs\SendEmail@SchedulePDF', ['emails' => $emails,"date"=>$date]);