Dear cindyh26,
Welcome to the Microsoft Community.
After reading, I have a general idea of your problem. I think your problem is related to the fact that Outlook's basic authentication has been deprecated and this is the latest public announcement from Microsoft.
Have you configured your Microsoft domain account (outlook, Hotmail, msn, live) as IMAP or POP? This is not secure and would cause the mail service to malfunction, please re-add the account via an automated process to enforce modern authentication.
On iPhone,
1. Go to Settings > Email.
2. Tap Account, then tap Add Account.
3. In the Add Account dialog box, choose Outlook.com.
If removing and reinserting your account doesn't resolve the issue, do the following:
1. Remove the account again.
2. Go to Settings > Safari and tap Clear History and Website Data.
3. Restart your iPhone.
4. Re-add the account and proceed with the Outlook.com account sign-in flow.
To sum up:
- If Outlook is configured to connect to Outlook.com using POP or IMAP:
You are often asked to enter a password for authentication, so that your account cannot be used normally. You need to add the Outlook.com account again using automatic account configuration instead of POP/IMAP and SMTP, after which OAuth is added to the account.
- If your email app doesn't support OAuth, use another one.
This is usually not an issue to worry about, as most major email apps, including Apple Mail, New Outlook, Thunderbird now allow new authentication methods.
Of course, if you're still having trouble adding your account in Apple Mail, you can also download the latest version of the Outlook app.
Please feel free to contact me if there are any further updates on this issue, I am here to help you further if needed.
Best regards
Yolanda - MSFT | Microsoft Community Support Specialist