in the past, people who had this kind of issue with the spam check results realised that they need to change their email subject
Unfortunately, we can't influence on spam check results or say anything more helpful. Spam check is an external service that we use and the only way to find more insights in this kind of issues is to try to contact spam check service support directly.
Can you try to change your email subject? If that doesn't help, then please try to contact spam check service support and ask them what to do about this problem.