Technical Video: Where does spam come from? By Desmond Liao | 1 minute read On September 30, 2010, MailChannels CEO Ken Simpson talked about how email spam gets sent out onto the Internet. In video 2 of a 5-part series, he answered: Where does spam spam come from? The short answer, botnets through three key channels: – directly out through email servers via port-25 – sending out through the ISP’s mail relay – compromised webmail Learn more about the Outbound Spam Challenge.