The suit against RIM ended with a $612.5 million settlement in 2006.
Targets of the new lawsuits did not immediately respond to requests for comment. The lawsuits were filed Thursday afternoon in U.S. District Court in Richmond, Va.
NTP was founded by Thomas Campana, an inventor, and Don Stout, a lawyer. Campana worked on wireless e-mail technology in the early 1990s, but never commercialized the technology. He died in 2004.
In the aftermath of the RIM settlement, NTP's patents have been re-examined by the U.S. Patent and Trademark Office, and many of their claims have been thrown out. But three of the 10 claims that RIM were found to have infringed were upheld, said Stout, NTP's president.
"Now we have to move forward," Stout said. "We hope we can resolve these cases without having to go to trial."
In 2006 and 2007, NTP sued the nation's four largest wireless carriers -- AT&T Inc., Deutsche Telekom AG's T-Mobile USA, Sprint Nextel Corp. and Verizon Wireless -- and phone maker Palm Inc. over the same patents. Those lawsuits have neither been settled nor come to trial.
