That's what I'm scared of each and every time I need to mail large amounts of gold to alts for epic flying or stuff.
Been talking to a GM about it. He said I should use ingame mail to transfer gold, instead of the guild bank or trade window. And in case of suspension, to mail wowgm@blizzard.com (or something like that, can't remember the exact address right now). There isn't much else you can do i guess. :(