What are email server settings for my iCloud email account?
For information on iCloud mail server settings, please see

Do you have iCloud Two Factor authentication turned on by any chance? If you do, you will need to generate an App-Specific password in order to connect to the iCloud SMTP server. See steps below:
1. Log into iCloud.com
2. Scroll to "Security" section
3. If "Two-Factor Authentication" is turned on, please click on the "Generate Password" link located next to App-Specific Password
4. Enter the password generated into the password field in the app