Problem with hidden field

I want to get, save and send specific information in a form with a hidden field. The field name is “info” and the value is retrieved with {get:infotext}. I can see the value ist shown correctly in the HTML of the website, but it is not saved or shown in the database after submission nor is it sent in the email (not with {summary} nor with %info%). When I change the field to a visible field type everything works well.

How can I achieve this with a hidden field?
Thanks for help.