A few days ago, a Texas-based company called InNova Patent Licensing filed an infringement lawsuit against 36 well-known companies. The company claims to hold the patent on spam filtering, and appears to be resting on the notion that any company using spam filtering owes them.

Among the companies being sued are Google, Apple, AOL, Dell, HP, RIM, Yahoo, McAfee, Symantec, and Siemens. The list doesn’t stop at tech companies though. It also contains names like Frito Lay, Cinemark, J.C. Penney, Rent-A-Center, and Dr. Pepper.

Chad Catacchio at TheNextWeb points out that Microsoft is strangely absent from the list, though one of the publication’s commenters points out that many of the companies named have offices in the InNova’s area.

"Email as we know it would essentially stop working if it weren’t for InNova’s invention," says InNova lead counsel Christopher Banys. "More than 80 percent of email is spam, which is why companies use InNova’s invention rather than forcing employees to wade through billions of useless emails. Unfortunately, the defendants appear to be profiting from this invention without any consideration for InNova’s legal patent rights."

Mike Masnick at TechDirt had some fun with this one. "First of all, actual spam filtering is a hell of a lot more sophisticated than the methods in this patent, and the idea that email would stop working without this patent existing is pretty laughable, he writes. "This is such a basic concept that it boggles the mind that anyone thought it was patentable."

The patent, granted to InNova’s founder 15 years ago, is titled "System for adding to electronic mail messages information obtained from sources external to the electronic mail transport process." You can read it here.