In our Marketing Cloud's data model, we have defined a unique ID for each user (subscriber), but it is possible that we have the same email address for different IDs.
We currently do not have a publication or subscriber list in place and use Data Extensions to send our emails.
Recipients have reached out to us and complained that they still receive emails even though they have unsubscribed many times. When I search for their email in the All Subscribers list I notice that they are right. There are more than one record with different keys but the same email address.
What is the best way of handling this situation? Should we set up an automation to unsubscribe all contacts with the same email address as soon as they unsubscribe from a mail?