Good job but not really hacking. It's just tricking your friend or one dumb mother fucker.
Honestly if you are about to get in to someones email and you randomly come out with that question I am sure 99.9% of the people are not going to give you that answer. Also, alot of email now like Hotmail for instance require you to give the persons address/postcode etc of there address, now honestly if you go to that person and ask them what there SA is and there addresss is then alarm bells should start ringing, if not then they deserve to get hacked.
I aint slagging you off I am just trying to be a realist and get the better side of the picture in saying that this aint hacking and your victim has to be one dumb mother fucker.