Hi, Jiří,
at first you should create an SMTP integration. You can do it via Main menu -> Create new -> Integration and select SMTP Client. Then, when you create it, you have to configure the connection details like hostname, port and optionally authentication options.
Next you should create a new action. In action editor you will find your SMTP integration in the right panel. When you expand it there is a Send email function. Drag it and drop it to the center area. Connect the Start node with your Send email node. Then when you select the Send email node you have to configure it via inspector (right panel). You have to provide recipient details, subject, body and optionally other parameters. Also, you can bind any properties (eg. recipient address) to action parameters to make them dynamic.
When you have it all done, you can test your action via Tester panel. Just click on the Save & Run button. If all configured properly you should see the success response (means no error and empty object on the output).
You can se an example configuration below.
If you have any problems, let us know!
