The best and easiest way is to copy the folder
X:\System\Mail
into a buffer place (like on computer) and then replace it in the new phone.
X is either C if he'd been using the internal memory as the storage place for sms's, and it's E if he'd been using the memory card.
I guess he'd been using the memory card, so the best way to carry out this procedure is to use a memory card reader.
Btw, This can only happen if the new mobile is a smart phone (Symbian).
Shayif el kher

Take Care