Unable to add "mbox" in actor of learning locker

I am working on a .NET core application and using learning locker. I am using TinCan API to communicate with learning locker. The code which i was using for creating the actor for learning locker statement was:

public Agent MakeActor(bool anonymous)
{
    return new Agent
    {
        name = anonymous ? AnonymousUser : UserName,
        account = new AgentAccount
        {
            name = anonymous ? AnonymousUser : UserId.ToString(),
            homePage = new Uri(StringHelper.ResolveHostName(Name,AwsDefines.AwsDomain))
        }
    };
}

Now i also have to add user email address in the records. What i got from google is that there is an "mbox" field in the actor which can be used for adding email address. So i updated my code:

public Agent MakeActor(bool anonymous)
{
    return new Agent
    {
        name = anonymous ? AnonymousUser : UserName,
        mbox = UserEmailAddress,
        account = new AgentAccount
        {
            name = anonymous ? AnonymousUser : UserId.ToString(),
            homePage = new Uri(StringHelper.ResolveHostName(Name,AwsDefines.AwsDomain))
        }
    };
}

Now i have my email address in the mbox field of actor but when i save the statement and see it in the learning locker, the "mbox" field is not saved, the "mbox"field is even not present the actor.

Any help will he much appreciated.