Google new feature called Gmalify that offers best of Gmail to Outlook and Yahoo users. This feature right now restricted to outlook, yahoo and hotmail accounts, but they have a plan to add more email services in future. This feature launched for certain email that do not require @gmail.com to somehow prevent spam.
If you have a Gmail account login to your Android App or Create a new Gmail Account first, If your using third party email inside Gmail Android App, you’ll just need to enable this new feature called “Gmailify” and done.
After activating this new feature you have to sign in to linked Gmail address that you see messages from other provider in your mailbox, and you’ll be able to read, reply, and organize your external mail just like you do in Gmail.