mihha Thanks for your response but I am not referring to the unsubscribe link.
First of all I am using the described unsubscribe link in the link you posted and YES it DOESN'T communicate with Acymailing. The unsubscriptions done via that link does not reflect in the Acymailing user dashboard. It only unsubscribe users from Elastic Email.
Secondly, I am referring to when the user marks the email as spam. The said users never unsubscribed but marked the email as spam.
I am guessing Elastic Email caught this and used their unsubscribe link to automatically unsubscribe the user but as Acy6 doesn't even register the normal unsubscribe process, it probably would not be able to handle this too.