The email has been around for the past 40 years, according to wiki, protocol has been introduced in 1981 and is still in heavy use. There is no shortage of various means of communication, however, when Facebook choose to take unexpected rest nothing stopped.
And email continued to work. It has been working steadily since 1981 and will be years to go. Nothing modern can be compared to something that has gone through the fire, water and any possible challenge. It reminds me of a Russian military radio station, you can crack nuts with it, riddle it with bullets and no matter what it continues to work as if nothing has happened at all.