If you want to backup your iCloud email using third-party utility, then you will need to generate app password.
Follow this Official iCloud Mail link to understand complete process
https://support.apple.com/en-us/HT204397
Following are the steps to create iCloud Mail App password
Do you want to know the IMAP/ Mail Server settings of iCloud Email Client?
Given below are the iCloud Email IMAP settings that you will need to setup iCloud Email account in any email application or email service.
Email Settings | Port Number |
iCloud IMAP Incoming mail server: imap.mail.me.com |
993, requires SSL 143, non-secure |
iCloud SMTP Outgoing mail server: smtp.mail.me.com |
587, requires SSL 465, non-secure |
Two factor authentication provides an additional layer of security when you access your account on multiple devices, like a mobile phone and computer system.
To generate and use app-specific passwords, your Apple ID must have Two Factor Authentication enabled.
Check the complete Guide for enabling Two Factor Authentication in iCloud/ Apple ID: https://support.apple.com/en-in/HT204915