Shaunmac here's a few links to Stamps.com US regulatory filings to enable you to DYOR here on the competitive landscape here.
The 10-K for fiscal 2017 should be out in early March which generally provides a far greater level of detail than the 10-Q's on operating matters and the market in general.
I find that these 10-K filings provide a great way to do some basic due diligence when DYOR
Off the latest 10-Q Stamps.com has the following math :
Revenue (annualised) of US$460m
Operating cashflow (annualised) of US$198.7m
EBIT (annualised) of US$142.6m
MV = US$3,615.0m
EV = US$3,564.4m
EV/Op Cash flow = 17.9X
EV/EBIT = 25.0X
https://www.sec.gov/Archives/edgar/data/1082923/000114036117041670/form10q.htm
https://www.sec.gov/Archives/edgar/data/1082923/000114036117010000/form10k.htm