I used the script described here, https://forum.acymailing.com/d/92-acymailing6-and-breezingforms, to sign people up to the newsletter, and it works.
However, I get an error 1062, Duplicate entry 'firstname.lastname@example.org' for key 'email_UNIQUE', if the peson who tries to sign up has already subscribed. This may well happen because many people unfortunately do not confirm their subscription by clicking on the link in the double opt-in confirmatiand on email.
How can I test to see if the person is already subscribed?
Or can it be made possible for the user to try to subscribe again without generating an error?
Note that I currently have "Allow user data modifications without identification" set to "Only their subscription"
Sorry, I see this has been asked already. Will look if there is a solution.