When creating marketing emails, you add the "Link for Customer to block all future emails" in the email content. If the recipient decides they no longer wish to receive related emails or wants to unsubscribe, they can simply click on this link, and the system will mark their email as an invalid mailbox, and they will not receive emails from you again.
 

If you want to check the list of invalid mailboxes, you can refer to this FAQ.

After clicking the block link, the customer will be labeled as "Email blocked by Customer," and you can click on the label to view the list of customers who have blocked receiving emails.