I have a simple one-page form (name, address, etc). I would like to export the data of the submitted webform by the user into CSV / XLS files.
How do I do that?
If you are using the webform module you can download submission's results in csv/xls files. if you want to do that go to:
content => select the webform you need to export => click on the result tab => finaly click on the download button.
If you need more flexibility like exporting multiple webforms Which fulfill certain conditions.
Take a look at the Forena Reports module and this post in which a detailed exemple is given by a co-maintainer of the forena module.
Just to add information to HusterFrancis posts. People who who feel limited by the core contact functionality in Drupal 8. There is a beta version webform 8.x.
Works very well. It does everything from scratch. (Export of data input, conditional rules, e-mail handling, etc)