There is nothing quite like bringing pen to paper, sending a letter away to someone special and patiently awaiting the reply. Every word you have has meaning, there are no backspaces, spell checks or instance responses. It's a great time to engage, be present and reflect. Unfortunately, however, you're unlikely to have a stamp (do they even exist anymore?) and you may get him up by the POPO in attempting a delivery BUT you can always stockpile. Just imagine the look on great grannies face down the line when she receives her surprise.
Why not try an online Pen Pal service such as this. It's free, safe and friendly! There are plenty of others but just be sure to check their credentials. The last thing you need is "Sally" saying your her long lost relative and next in line for the family fortune... you just need to "send you bank account and IRD number".