Thank you for your suggestions. This is not a Microsoft account. It is an email server (hosted by Hostway on an Exchange 16 server). I can send/receive emails from my MBA Ventura 13.3.1 using macOS Mail app. I can send/receive emails from iPadAir iPadOS 16.3.1. But suddenly, just other day, my iPhone 11 Pro iOS 16.4.1 using iOS Mail app, it stopped sending and receiving. (I have tested all three devices) As I mentioned, I tried deleting the email account and reinstalling it (multiple times). But to no avail. The Mail app settings in both the iOS and iPadOS are exactly the same (macOS is different). I have confirmed that the settings are the same. It's a puzzle to me. My anecdotal observation is that the only thing that changed was that iOS updated.
I just noticed that iPadOS has an update available (16.4.1) which appears to make it equal to iOS. I'm about to install it. It that kills the ability of that email account to send/receive, then I think that suggests it may be a new protocol that communicates with the mail server that is causing the problem. I'll keep you updated. (BTW, I also have an Apple .Mac email address hosted at Apple and a Microsoft Hotmail email account hosted at Microsoft and a Google Gmail email account hosted at Google and all three of my devices have no problem sending/receiving. It is only the independent domain email address hosted at Hostway on an Exchange server that is having a problem with iOS Mail app.
