How a Snail Mail Startup Bust Shaped One Serial Entrepreneur Learn how an engineer learned the value before building the product.

Jonathan Siegel has launched 20 companies. Two led to eight-figure exits -- hooray! -- and 16 went bust. But one failure from 2005 informed a success a decade later. The flop was PostASAP, which sent letters for users who didn't want to deal with printing, envelopes and the post office. It died in a year. Today he owns Earth Class Mail, a $5 million platform that scans, shreds or processes businesses' snail mail. Here's how he got from one to the other.

Q. What was the first sign of trouble for PostASAP?

A. The week after we launched was an amazing letdown. We got some press and plenty of traffic, but nobody was signing up and staying. At the time, people weren't as comfortable invoicing or writing important documents online. And they didn't want to pay a premium for the service.