Email fetching delays on my iPhone Mail app post iOS 18 update

The native Mail app on my iPhone 16 Pro with iOS 18 is not fetching my Yahoo mail account every 15 minutes like I have selected in the Settings. When I go into the Mail app and refresh, emails populate that are multiple hours old. I also know I have new emails because there is a badge notification icon on the app tile on my home screen but I do not receive any push notifications (yes I have that configured correctly in Settings). Never had this problem on my iPhone 12 with iOS 17 that I traded in. Anyone with similar issues or a solution?

[Re-Titled by Moderator]