List<Message> result = new List<Message>();
UsersResource.MessagesResource.ListRequest request2 = service.Users.Messages.List("me");
do
{
    try
   {
          ListMessagesResponse response = request2.Execute();
          result.AddRange(response.Messages);
          request2.PageToken = response.NextPageToken;
    }
    catch (Exception e)
    {
           await ReplyAsync("An error occurred: " + e.Message);
    }
} while (!String.IsNullOrEmpty(request2.PageToken));
foreach (var msg in result)
{
     Console.WriteLine("[" + msg.Raw + "]" + ";" + msg.ToString());
}