When you want to checkout a high demand item on Bestbuy you have to login again to verify your purchase. During login Bestbuy will email you a code which you have to use in order to checkout.
IMAP enables Kuai to read your emails so the bot can get this code by itself.
Example of an Email sent by Bestbuy to verify purchase
How to setup IMAP?
Kuai only supports Gmail emails at the moment
Login to your gmail account
Click on the gear icon, than click on See all Settings