If you have the problems with your connection via Yandex account, please follow these steps:

  1. With two-factor authentication enabled (and even if you disabled it for third-party apps), you need to get special passwords – you can do this in the "App Passwords" section on the page https://passport.yandex.ru/profile/.

    NOTE: Application passwords are needed even if two-factor authentication is already disabled.

  2. You need a password for the application type "Mail (POP3/IMAP, SMTP)").

  3. Please note that you will need to insert a password in IMAP settings.

That's all. You can use Yandex IMAP with App in the Air.