Does anyone use this? To me it sounds like something out of Shakespeare. Seriously, most letters or emails these days can be signed off with "Thank you," or at the most, "Sincerely,"
As always, I'm open to the possibility that this could be a lot more popular in some other population of English speakers, like in Britain or among college professors. But in American English, for casual or normal business use, "Verily yours" sounds ridiculous.