Blocking Legit Emails

I ran into some issues with this plugin…
Of recent, I’ve noticed that CleanTalk is blocking or preventing emails from going through from LEGIT users and marking them as SPAM instead. Is there any reason for this? I can’t seem to understand why this is happening. The emails are being sent from LEGIT users, and NOT spambots.

Is there a way to prevent this from happening?

Please advise on a solution.

Thanks