Fresh off its record win over Research in Motion, push-messaging patent-holder NTP is setting its sights on bigger fish, or whales rather. This time it’s taking on the giants of the telecom industry, suing AT&T, Verizon Wireless and Sprint.

Just as in the RIM case, which rewarded NTP with a $612.5 million settlement, NTP is suing the operators for patent infringement related to messaging technology it developed before push e-mail became a monster application in the last few years. NTP is asking for royalties based on phone sales, but the lawsuit doesn’t apply to all of the companies’ devices. They would affect only those that use push e-mail services, and RIM’s BlackBerry, Motorola and Nokia devices would all be exempt since they all have licenses with NTP.

But both Samsung and LG produce a vast number of devices for those three carriers, including high-end smart phones with push e-mail capabilities. Palm may be another target; its Treo lines all contain native push e-mail capabilities. NTP has already sued Palm, though the case has been put on hold until the U.S. Patent Office conducts a review of NTP’s patents. The lawsuit against the carriers, however, may represent a change in strategy for NTP. Instead of suing the device manufacturers, it is going after the carriers whose networks power the push-messaging services. When Qualcomm became subject to a chip ban from the U.S. International Trade Commission for infringement on Broadcom’s patents, Verizon Wireless took out a licensing agreement directly with Broadcom.

The basis of NTP’s case may be under threat from the Patent Office’s investigation. While the patent office has declared some of its patents nullified, NTP has appealed, leaving the patents valid until the case is finalized.