Sharepoint - REST expand people column

Try AssignedTo/EMail....case sensitive.

Available values from a user field (Source):

Title

Name

EMail

MobilePhone

SipAddress

Department

JobTitle

FirstName

LastName

WorkPhone

UserName

Office

ID

Modified

Created

ImnName

NameWithPicture

NameWithPictureAndDetails

ContentTypeDisp

On SharePoint Online, to get the login name (account name) from a user field in a list, you need to select the Name property:

.../_api/web/lists/getbytitle('ListName')/items(60)?$select=MyUserField/Name&$expand=MyUserField

This returns the account name in the format i:0#.f|membership|[email protected]. You'll need this value if you want to query the user profile service for more info on the user.

I believe by using the person type field you are limited to the fields mentioned in the blog you linked. You can however make a rest call to get a person's UserProfile properties.

Vardhaman has a great post on what properties you can access and how to do it.