Nobody wants to be spammed - and spam is a growing problem, with 14.5 billion spam emails being sent every single day
. In fact, 45% of all sent emails are spam, making it the most annoying form of communication. Starting way back on USENET in the early 90s
, even improved spam filters do not completely prevent spam (and can sometimes block legitimate emails, causing frustrated users to turn them off).
Because of spam filters, it is cheaper for spammers to infect a machine with malware, send spam from it for a while, then switch when it is blocked - the DNSBL
database will block the IP of an infected machine after a while. This results in the extra annoyance of your customers receiving spam that appears to be from you. It can also result in your server being blacklisted and your own email being blocked as spam. Sending spam is made even easier by standard SMTP protocol not requiring verification of the sender.