sending notification on incoming email

[shalmaxb]

Hi, how would it be possible to send a notification to a user on incoming Email to a custom group folder?
I have an entity from which I send an email to a customer. This entity would be parent to the email sent and that has the assigned user from this entity. When an answer to this mail comes in, it is linked to the former parent and assigned user. I would like to send a notification (preferably also by mail) to this assigned user.