These configuration values are set on the PwnageNotifier class and can be overridden in your project's config.yml in the usual Silverstripe way.
The default value for email templates is:
system-ui, BlinkMacSystemFont, 'Noto Sans', Helvetica, Arial, sans-serif, 'Noto Color Emoji', 'Apple Color Emoji'
Change value to be the email address notifications will come from
e.g "[email protected]"
Default: noreply@localhost
Change value to be the name emails will come from e.g "My Company Security Division"
Default: 'Account notifier'
Email templates can be overridden in your theme, just copy the module's include and template files to the same path location in your theme/<theme_name>/templates or app/templates directory and edit as required. See https://docs.silverstripe.org/en/5/developer_guides/templates/template_inheritance/ for more information.
The templates shipped with this module are provided as a guide.