An antispam system that works well today will slowly lose its potency as the spammers learn how to evade it. Large organizations can dedicate the time and money to stay current with their antispams technology, but small companies generally cant. Spammers have the upper hand in this cycle, says author. Spam filtering is not something that you can set up and forget, he says. An estimated 1 million to 100 million infected computers in the world today, he writes.”]
Source: https://www.csoonline.com/article/2122580/spam–a-lot.html