SharePoint Online people picker issue

Hello  Group,

Need an urgent help. How do I update a people picker field using POSTMAN? I have done that though PS script, C# using REST API. Used EnsureUser Object to create a user object that can be passed on the people picker. 

I have the Office365 email that I need to update/insert into SharePoint online people picker using POSTMAN. 

I think email string cannot be directly assigned to the people picker.

Any hint/suggestion would be of create help.

Aniruddha