I created a Backend Module to configure the extension. The user is now able to type in the e-mail address to which the auto-generated e-mail is going to be sent etc.
Unfortunately, there is a header in the Backend Module which contains a dropdown (
In general it is helpful to know at least the version number of TYPO3 as e.g. 6.2 is a lot different to 7.6 and 8.
Without knowing your extension's code, check out either the template which can be found in
Resources/Private/ or the controller inside
Classes/Controller/<Domain>Controller. One of those 2 places should contain the unwanted html.