Apple's Mail app has introduced a new inbox categorization system in iOS 18, allowing users to manually categorize senders' messages. This feature was initially a problem for many users, with several instances where senders were not included in the categories. The feature allows users to select which category their messages will go to, allowing them to have all communications delivered to one. The new system also allows for email messages to be sent to a specific category, allowing for more information about important individuals to be notified.