Thanks for your prompt reply!
I had already read the documentation. What I don’t understand is how to indicate the automatic reference to the ‘html’ and ‘txt’ version of the template.
If I use guide syntax I have to refer to a specific file:
'media' => __DIR__ . '/emails/media.php'
In the example that is given in the guide section “HTML & Plain Text” $kirby->email(['template' => 'media',... has the ability to refer to “two” files emails/media.html.php & emails/media.txt.php