The Stamford, Conn., company, with clients including 90% of the Fortune 500, said that a malware attack "encrypted information on some systems and disrupted customer access to some of our services."
But Pitney Bowes also said in a Monday statement that it saw "no evidence that customer or employee data has been improperly accessed."
Systems in the affected areas are being restored by a third-party consultant the company employed, Pitney Bowes said.
Pitney Bowes shares finished up 1.4% at $4.46. They traded on Monday as low as $4.28, down 2.7%, and as high as $4.50, up 2.2%.