It is likely that someone may have made a typo when typing the email. (For example, someone using abc123@kakao.com may have typed it as abc@kakao.com, and the email will be sent to the actual owner of the abc@kakao.com account.)
On the notification email, click the link "If the Kakao Account is not yours, please click here."
When you delete the email address by clicking the link, the person who used that email address to sign up will receive an email to change his/her email address.
If you want to make sure that the email address is not used for any Kakao services, please capture a screenshot of the concerned email and attach it to a request to our Customer Service with a title "Do Not Register as Kakao Account Email."
Please beware that once you send this email, the concerned email address cannot be used for Kakao Account by anyone including yourself.