Deleting email messages - Thunderbird vs Apple Mail

I use a Windows 10 or 11 laptop with Thunderbird installed as the email client app. My wife uses an iPad with Apple Mail. We have separate accounts using Spectrum's email servers. My Thunderbird client automatically downloads and permanently deletes email messages from the Spectrum server when I tell it to get messages. My wife's Apple Mail client downloads the messages from the server but does not trash or permanently delete them; they thus pile up and cause her email flow to stop due to overcrowding. How do I get her Mail app to permanently delete the messages from the Spectrum server once they're downloaded?