Fetching plain_text Main - missing direct_mail boundaries (TYPO3 11, direct_mail 8.0.0.-alpha)

[ineswillenbrock]

TYPO3 11.5.17 direct_mail 8.0.0-alpha PHP 7.4.30 User is Admin and has the rights for the install-tool. Both direct_mail static templates are included.

And another one:

Creating a new direct_mail Newsletter

selecting Direct Mail -> click on the storage folder with the plugin -> choose Internal Pages -> Create a new newsletter -> choose both Plain Text and HTML format

results in a Warning:

Check the following warning.

The plain text content does not contain any direct mail boundaries.

When trying to view the page with the type=99, it uses the configured template but gives no hint towards the boundaries.