Twig naming convention for Webform emails

I don't know about webform module specifically. In general, please see docs https://www.drupal.org/docs/contributed-modules/drupal-symfony-mailer/ge... → .

Thank you, Adam.
I have seen the docs, but I was not able to determine the correct template names.

It should follow the same pattern as swiftmailer, so I would expect email--webform--my-form-my-handler.html.twig. Could it be something silly such as need to clear cache, file in wrong directory etc??

Thank you so much!
The correct template name is indeed email--webform--my-form-my-handler.html.twig.
Perhaps it really was a cache issue (I've cleared the cache with drush - perhaps this was not enough).