Why do I need to add two or more data extensions as a source to data filter?
Sometimes we need to add customer or team member email addresses to an email campaign because they are not subscribed and don't need to subscribe to a specific campaign, but they need to receive an actual email the same as subscribers. My idea was to create one data filter which has two or more sources - one data extensions with actual subscriber data and another one for custom email addresses which can be added and removed any time. If someone knows a better solution how to do this, please chare. The solution to select two data extensions instead will not work, cause emails will be sent through API.