Scrolls of Mail

Sometimes when I'm playing on Hardfought or NAO, someone goes to the trouble to send me a scroll of mail. But when I read it, I get presented with (as far as I remember) a black box (maybe containing black text, who knows?). If I want to read scrolls of mail, is there an option I need to set via shift-O or the rc file, depending on the variant I'm playing? I feel like since the Devs implemented it, the server permits it, and the variant supports it, that I should be able to read the darn things!

Or maybe that's the gag? Someone is trying to drive me mad by sending purposefully blank messages? Probably in retaliation for my boring and grinding playstyle?