Mass mailing might be, but highly-individualised large-batch mailing? Every card distinct? Even if this is largely a holiday gift, I'm certain they're collect

Mass mailing might be, but highly-individualised large-batch mailing? Every card distinct? Even if this is largely a holiday gift, I'm certain they're collecting data on it. The only question is what. Maybe some of the cards will be "tracers" sent to confederates who can verify delivery times of things sent in big batches? Maybe they have multiple printing-and-distribution locations throughout the country and they're testing those? Who knows....