Mail not updating on iPhone 16

When I open the Mail app on my iPhone 16 Pro Max running 18.5 I find that no emails have downloaded since April 24, nearly three months ago. There have been no problems with the Mail app on my desktop Mac Studio. I deleted a massive amount of old emails to ensure this was not a capacity issue. That made no difference. No new emails show up on my phone although they do on my desktop. Maybe I've mis-configured it somehow. But I don't know where to start.