Have you signed up to for an invite to Inbox by Gmail (formerly Inbox by Google, apparently)? It looks like public invitations to the service have begun rolling out.

Be sure to check your Gmail if you signed up. If you haven't, email inbox@gmail.com to get put on the waitlist, but if you signed up yesterday you should probably be seeing an invite shortly.

Inbox by Gmail (Playboard) | Inbox by Gmail (Play Store)

[PSA] Waitlist Invites For Inbox By Gmail Are Going Out Now was written by the awesome team at Android Police.