Lob, a San Francisco, CA-based builder of a suite of mail API for the enterprise, raised a $20m Series B funding.Along with this funding, Ali Rowghani, CEO of YC Continuity and former COO of Twitter, will be joining our board.The company intends to use the funds to accelerate growth, expand its core API offering, and grow its team.Co-founded by Leore Avidar and Harry Zhang, Lob is building a mail API that enables companies to send postcards, letters, checks, photos, and more.Lob has over 6,000 customers including Amazon, Oscar Insurance, & Booking.com.