Hello Stefano,
First of all, I wish you a happy 2020. The Newsletter plug in is excellent and I am thinking about buying the Premium Plan, but there is something important I would like to fix first.
I have designed a double opt-in subscription form and when using the confirmation_url parameter, the subscriber is redirected to the confirmation_url as welcome message, not as confirmation – which destroys the double opt-in protocol, as real welcome page does not appear and the confirmation email link redirects to standard confirmation page, and not to confirmation_url as it should do.
I have checked that the double opt is active in my subscription configuration page.
I have read the same problem not solved in this thread.
Here´s the form code:
[newsletter_form button_label="Go" lists="1,13" confirmation_url="https://www.website.com/selected-information/"]
[newsletter_field name="email" label="Your email:"]
[newsletter_field name="privacy" label="I read and accept the privacy policy"]
[/newsletter_form]
Thanks and kind regards.