Allow Recipients to Unsubscribe from All Emails
Follow this tutorial to include an unsubscribe link in promotional emails sent from Salesforce. This post gives you some reasons for considering this feature.
When the recipient clicks to unsubscribe, a flow will look for all contacts and leads who have this as their preferred email address (if you’re in NPSP) or in the Email field. All contacts or leads who meet that requirement will be marked “Email Opt Out.” The email address owner will receive one confirmation email immediately.