With Gmailify, you can now use Gmail without a Gmail account that’s Google is letting you use its service even if you don’t have a valid Gmail email address. That’s being said, you can log into Gmail client with a Hotmail or Yahoo email address.
Gmailify links your existing account to Gmail so that you get all the bells and whistles—spam protection, inbox organization and even Google Now cards based on your mail—without having to leave your current address behind. All you need to do is open the Gmail app, sign into your email account, and enable Gmailify. And of course, you’re always in control—so if you ever change your mind, you can unlink your account(s) at any time, and continue to access them through the Gmail app without using Gmailify.
As of now, Gmail supports only Hotmail and Yahoo email address, and Google is planning to roll out this feature to other email providers in the future.