Problem Reported: 

User got the email from the email ID of the organization which is already deleted.



The sender Email ID(Non-existent/Deleted) is a alias of user “email ID”(Existent). The alias ID can be used for the authentication while sending the mail and it can also be configured in applications.



The alias ID authentication can not be removed, if you don’t want the alias ID you can remove it using the Admin Panel console.