The Spamhaus is a project enlisted by an international organization with offices in both London and Geneva. It was founded in 1998 by Steve Linford to track all kinds of email spammers and other spam-related activities.
22 years later, still whenever an IP address is apparently involved in spamming, they’re immediately listed on Spamhaus Blocklist aka SBL. In general these blacklists also known as Domain Name System-based Blackhole List (DNSBLs) analyze the IP addresses for its reputation. These measures are in place to protect day-to-day email users from deliberately opening spam emails and harmful links, which often displays suspicious activities or show up as click bait. These offending IP addresses are blacklisted on priority, as with lack of protection - web hosts and networks can be easily compromised and will be used to spam email users with tons of harmful emails.
So how does one make their way to a blacklist, how can you un-list yourself ???
One doesn’t simply become a spammer if they don’t have a humongous list of email addresses or stack of email databases. These lists are built by scraping the web to collect all email addresses, even the sales@, info@ and firstname.lastname@example.org. Emails are also purchased through unregistered, ‘underground’ marketplaces and also at times from other email marketers looking to make an earning.
Organizations like Spamhaus, SORBS. UCEPROTECT, and other anti-spam and blacklist entities use their secret weapon, a number of special email addresses known as ‘spam traps’ to catch spammers. These organizations intentionally showcase their spam traps, to get picked up by spammers and make a place in their address list. Once the traps are set for the spammer, the next step is to wait till the email addresses part of the ‘spam trap’ to get spammed. As soon as the malware initiates the spamming to the list containing the spam trap, as a first step it has inform the mail server, the email address it wants the message sent to - once the spam trap email is entered, the entire operation is compromised and the IP address of the spammer is added to the blacklist.
Although you as a normal user can also get your IP address blacklisted as many ISPs and hosting services dynamically assign IPs to users, meaning your IP changes quite a few times in a duration of hours, days or a week and is being used by other users too.
For Example: So, during this phase if user A has spammed anyone and his IP address is now dynamically assigned to User M, then this specific user will find his IP address to be blacklisted without even doing anything.
In such a situation, where you're sure that you or your system isn’t involved in any spam activity or affected by a malware, you can visit the blacklist removal pages provided by most IP blacklist operators, and request the removal of your address. Here are some links to the removal tools provided by a few of the more popular IP blacklists: