Double OptIn and Spamfilter "Session check" gets flagged as Spam after confirmation on a new device

[BokuNoMaxi]

We recently found a problem with one of our newsletter forms. For these forms, you need to confirm that you want to subscribe to the newsletter. The problem occurs if a user tries to subscribe from a new device that has never opened the page before. To reproduce the problem::

1. Create a form with Double Opt-In enabled
2. Submit the form
3. Open a private tab and paste in the link from the Confirmation Mail
4. 

Why is this important?

For example, I'm on my desktop and then I want to submit a form on a website.Most people will fill in their Gmail or Apple Mail address. But as soon as they see that they have to confirm and check their emails, they'll open the Mail App on their phone.Then they click on the link and a big red box appears saying that the form they just submitted is spam. In the background, the code malfunctions, and the email gets flagged as activated. However, because of the error, no further emails will be sent to either the receiver or the submitter.

Tested with

typo3 12.4.23 and 12.4.25
powermail 12.5.1 and 12.5.0

Error