Just to provide some clarity to Imoody's last post:
This is a little known bug and not something that development is going to fix at this time.
When the SmarterMail interface was first designed many iterations ago, zooming was not an option. Most of the interface layout uses fixed positioning, etc. To change this behavior requires a significant overhaul and redesign of the current interface. The development team and management realize the current limitations our interface. As such, we will be making changes to the interface over the next few releases of SmarterMail (along with changes to the other SmarterTools products). The specifics for what interface features (for example, zoom handling) will be changed and in what new version has not been fully detailed out yet. This is the reasoning behind Imoody's comment that "this is a little known bug and not something that development is going to fix at this time."