Stamps.com Inc. /zigman2/quotes/202777086/composite STMP -1.08% shares soared 20% in after-hours trading Thursday after the internet-based mailing and shipping service reported fiscal second-quarter revenue that blew past Wall Street estimates. Stamps.com reported net income of $51.7 million, or $2.73 a share, compared with net income of $14 million, or 79 cents a share, in the year-ago quarter. Revenue jumped 49% to $206.7 million from $138.8 million a year ago. Analysts surveyed by FactSet had expected net income of $1.26 cents a share on sales of $153.3 million. Stamps.com shares are up 214% this year. The broader S&P 500 index /zigman2/quotes/210599714/realtime SPX -0.40% has improved 3.7% in 2020. Stamps.com's big quarter comes amid a national slowdown in postal-service deliveries.