Why is there an error message for my iCloud mail account on iPhone and when I’m signed into mail and try to send an email it won’t send it goes to outbox

My iCloud email does not work. In settings under mail it says an error message and I’ve deleted the mail app and reinstalled. And when I login it does not let me send emails. It just goes to outbox. I have iCloud+ and have made alias email addresses. Don’t know if that’s the issue. But I’ve also tried using the different alias emails to send an email and does the same thing. Also when I try to sign into my Apple account on Apple.com or iCloud.com it signs in then immediately goes back to the sign in page. I’ve tried logging out. Disabling. and re-enabling iCloud mail and changing the password several times. I’ve also uninstalled and reinstalled the Mail app several times and nothing seems to work.