Are there any settings in the Email app related to downloading attachments? In the Gmail app, there's a setting for "Download attachments," but that selection is to "auto-download attachments to recent messages via wi-fi." I'm don't use a stock Email app, so I don't know if there might be a setting on Samsung that I'm missing.
EDIT: Actually, I just checked my wife's Tab Pro. The stock Email app does have this setting, but I'm not sure if it will solve your problem.