KEY POINTS
  • The stock was down nearly 3 percent by Thursday's close.
  • The USPS has agreements with private companies providing specialized rates, but it can renegotiate or terminate those deals.
  • Prior to this disclosure, Stamps.com saw its stock price increase by 36 percent in 2018.
Ken McBride, stamps.com CEO and Chairman at the company's headquarter in El Segundo on Mar. 13, 2013. 

Stamps.com stock fell on Thursday after it disclosed that the United States Postal Service requested to renegotiate one of their key arrangements.

The stock was down nearly 3 percent by the close. It regained some ground since the morning, when it fell about 7 percent.