I have an argumentative contact on Zoho CRM who I no longer want to engage with but whose historical records I have to keep. 

I have created an Email Opt Out tick box in CRM some time ago and have a sync running to Campaigns for all contacts that excludes any with this box ticked. 

Today, I have sent my latest newsletter and to my surprise, this guy has received it and then replied. 

Why is he receiving my newsletter when I have the campaign and CRM linked and set up this way?

Does this mean that all contacts that I am marking as Email Opt Out are still receiving my communications, thus perhaps exposing me to breaches in the data protection regulations regarding the right to unsubscribe?