How to get a user's email address with REST API in SharePoint

When I was working SharePoint REST API recently, I just found one interesting thing about user column regarding a query in REST API. The thing is when you use a REST to query items which contains user columns, actually you can get a bunch of properties other than just user’s ID and Title. Here is a list of these properties I copied from Stack Overflow,

Title

Name

EMail

MobilePhone

SipAddress

Department

JobTitle

FirstName

LastName

WorkPhone

UserName

Office

ID

Modified

Created

ImnName

NameWithPicture

NameWithPictureAndDetails

ContentTypeDisp

So here is an example,

http://your-sharepoint-web/_api/web/lists/getbytitle('your-list-title')/items?$select=User/ID,User/EMail&$expand=User

With this call, you are going to get the user’s eamil in the JSON response.