There are two main ways that people can be unsubscribed from emails:
Self opt-out - via Unsubscribe link in a Campaign Email
Internal Global Unsubscribe opt-out - via 'Email opt in' toggle in a contact record.
1. Campaign Email Unsubscribe Link
When you send Campaign Emails, they will include a link that will allow your contacts to unsubscribe from Mailing Lists.
Depending on your App Settings, contacts can unsubscribe from individual Mailing Lists or all Mailing Lists.
This contact will automatically have an Activity Note added to their record saying that they have Unsubscribed. Email Campaigns that are sent to this person will NOT be sent.
However, Direct Email Campaigns sent to this contact WILL continue to be sent.
Why can you continue to send Direct Email Campaigns when contacts unsubscribe from your Mailing Lists?
Campaign emails, by nature, are marketing emails. They are the type of emails that you use to send newsletters etc. Your contacts have the right to remove themselves from these Mailing Lists at any time. However, you are still legally allowed to send 'legitimate business offers' according to GDPR/US CANN SPAM regulations, providing that the offer has not been sent to them before. This would naturally be sent via a Direct Campaign, hence why they have not been unsubscribed globally.
2. Global Unsubscribe - Email opt-out
In situations where you no longer want to send emails to a person under any circumstances, you will want to use the Global Unsubscribe.
Global unsubscribe is a system-wide unsubscribe which will stop all emails to a contact. To use this you simply need to access the contact record of the person you are looking to unsubscribe, and toggle the 'Email opt in' button to 'off'.
No further emails will be sent to that contact.
You can bulk update multiple contacts should you choose.