I view all my messages in the "All Content" tab
is like a quick reply option (No Advanced Editor Option),
and if you want to attach any files etc.. then you need to double click the original header
and it will take you to another reply option with the (Use Advanced Editor Option). The Advanced Editor allows you to attach different files or change font sizes etc...
If you click on the All Content Tab it will show the different thread and if you reply from there then you will be able to use the Advanced Editor..