ELI5: Explain Like I'm 5

DNSBL

DNSBL (Domain Name System Blacklist) is like a list of bad guys that your computer or phone can check before letting emails or messages from them come through. Imagine you have a secret message box, and someone wants to send you a message. Before the mailman delivers the mail to your secret box, he checks a list of naughty people. If the mail is from someone on the naughty list, the mailman won’t put it in your secret box, and it gets sent back to the sender.

Similarly, DNSBL is a list of IP addresses (a unique number that identifies a device connected to the internet) that are known to be sending spam, malware, or viruses. When you receive an email or message, your device checks the IP address from where it was sent against the DNSBL list. If the IP address is on the list, your device won’t let the mail through, and it gets sent back to the sender, just like the mailman.

In short, DNSBL is like a postal service for emails and messages to protect you from bad guys trying to sneak into your secret message box.
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