The Rapture was an idea concocted long after the Bible was written.

"This doctrine gained popularity in the 1830s, and more recently in the 1970s, with proponents of the premillenialist, and in particular the dispensationalist, interpretations of scripture.

There is much debate over when the rapture will occur in relation to the Tribulation, a seven-year period preceding the second coming of Christ to the earth. Three different views predominate. The first is that it will take place sometime prior to the Tribulation. The second is that it will take place mid-way through the Tribulation. The third is that it will take place after the Tribulation, when Christ comes to earth to establish his kingdom, taking over rulership of the world for 1000 years. (see Millennialism). A fourth view has recently developed, called the Pre-Wrath view."

As for that email, it's classic war propaganda designed to whip people up into a frenzy and send them out to kill. Such propaganda suits any government intent on making war. I'm sure the Nazis had such letters published in their press to stir them up, and I bet the Islamic Jihadists do also.