Why is there an exclamation mark next to the customer's email?

If there is an exclamation mark symbol next to the email on the customer's profile page, it indicates that the email is listed in the "Invalid Emails" section.

You can check the "Problematic Emails" by navigating to [Settings > Data > Invalid Address].


＊How can I check invalid email addresses?
＊How do I remove invalid email addresses from the system?