You should check with your legal team as different companies interpret spam laws. Best practices, is yes, if they unsubscribe for marketing emails that information should be passed onto yes ware, sales loft so that folks are not getting emailed by sales. I have experience many pissed off people that unsubscribed from Marketo and still received emails from sales.
We push the value from Marketo to SFDC into the Email opt out field and then into the sales enablement tools. Training sales to always use a filter to exclude these emails from their sends is also important.
The other issue I have encountered is with maintaining IP sender reputation. In marketo we stop sending to bounced emails but sales folks don't have this info, so we make sure we push this info to SFDC and they are also excluding bounced emails. With the wide availability of tools like outreach, tout app, yes ware, etc, I am seeing more bad IP reputation because of lack of governance.
Kill two birds with one stone and have sales folks exclude email opt out and bounces while you are at it.