Form to be entered into a database doesn't insert anything

I've configured a form to the database table "mailing" but it doesn't receive any input, even if the form itself plays back a success message:

`## Subscribe
subscribe:
templates:
form: 'partials/_subscribe.twig'
feedback:
success: Deine E-Mail Adresse email wurden erfolgreich eingetragen.
error: Die eingegebene E-Mail Adresse ist ungültig.
database:
table:
name: mailing
field_map:
mail: 'mail'
timestamp: 'lastseen_at'
url: ~
path: ~
ip: 'last_ip'`