Lob is a startup promising to help businesses deliver physical mail more quickly and affordably, and with more personalization. The company estimates that its platform has been used to deliver mail to one in two U.S. households. And today, it’s announcing that it has raised $50 million in Series C funding. CEO Leore Avidar told me he founded Lob with Harry Zhang nearly a decade ago to “allow people to send mail programmatically.” Over time, the company has become increasingly focused on enterprise clients — its 8,500-plus customers include Twitter, Expedia and Booking.com — although Avidar said it will always offer a product for small businesses as well. Avidar explained that in a digital age, there are two main categories of physical mail that Lob continues to support for its customers.