iCloud email?

If it's anything like how MS does it with Outlook, from your computer, log into your iCloud and go to Security Settings. Then look for an option to generate an application password. Once you do that just that one time, you can use it as the password from any email client that supports iCloud email. You don't need to remember this app password, because next time you get promoted for your iCloud password, you can just use whatever it is now if you haven't changed it.

App specific passwords are just a one time two factor authentication mechanism to increase security. One time setup and you're done.