This is weird.
OK, I understand the logic behind
Nigerian email spam: if you copy, paste, and email the same plea for help (and bank account details) often enough, you're going to find someone gullible enough to send them to you - even today, when most of us are all too well aware of these emails and know how to spot them the moment they drop into our inbox (if they don't get spamfiltered out before then anyway). I also see how, before this kind of spam started accounting for a sizeable percentage of all email sent and received, and especially before email became a major means of communication in the first place, people might still have fallen for similar messages from faraway countries when they received them in letter form.
But this? A hand-written letter from Uganda, basically containing the same standard text ("I warmly greet you in God's name", and all that), snail-mailed to my office address? Surely today, with the benefit of our added experience of spam scams, the hit/miss ratio just wouldn't make it worth the effort - spam emails are cheap and literally send themselves, but with handwritten letters you also have to cover the cost of manually writing and (air-) mailing them?