Serialization throws exception

Serialization throws exception

What i'm doing is to serialize class through background task and it throws
exception
Cannot serialize member 'BackgroundTask.BackgroundTaskDescription.Emails'
of type 'System.Collections.Generic.IList.
My class structure is shown below.
public sealed class BackgroundTaskDescription
{
public string Subject { get; set; }
public string Message { get; set; }
public string dueTime { get; set; }
public IList<string> Emails { get; set; }
}
How i implement this.? I need List for storing emails through background
task.