I have also learned it is good to hover over the senders information if the subject line is suspect. I have a friend who emails me every once in a while, but I always hover over her information because there are many times it isn't really from her. I can't open them and send them to her because the damage is done then.
I also don't open emails from people I don't know unless we have talked and I will tell them to put something special in the subject line so I know it's from them and is safe to open.