Four years after collecting a hefty legal settlement from Research-In-Motion (RIM), the manufacturer of the BlackBerry wireless email device, NTP Inc. last Friday announced the filing of a lawsuit against six smart phone makers that are accused of infringing NTP patents that relate to the wireless transmission of e-mail messages to cell phones. Filed with the U.S. District Court for the Eastern District of Virginia, the patent suit names Apple, Inc., Google, HTC Corp., LG Electronics, Microsoft Corp. and Motorola as defendants. The complaint also follows a similar lawsuit filed earlier by NTP against wireless carriers AT&T, T-Mobile USA, Sprint Nextel, and Verizon Wireless. (That suit has been stayed pending the completion of patent reviews by the U.S. Patent & Trademark Office.) To avoid an injunction against the marketing and usage of its popular BlackBerry device, RIM agreed to pay $612.5 million to settle patent infringement claims levied by NTP. Co-founded by Thomas Campana, who is credited as the “inventor of wireless email,” NTP has signed licensing pacts with Nokia Corp. and with e-mail systems provider Good Technology, Inc. that cover the usage of patents held by NTP. Commenting on last week’s court filing, a settlement negotiator with NTP explained that “there have been conversations with the people named in this suit, but they haven’t been successful.” Although five of the six firms named in the suit declined comment, a spokesman for HTC said his company “takes these matters very seriously.”