Blacklist monitoring tool for cloud-hosted IPs

What to build

A lightweight SaaS that continuously monitors a user's server IPs and ASN ranges against UCEPROTECT, Spamhaus, and other major RBLs, sends instant alerts on new listings before mail or traffic gets silently filtered, and provides step-by-step delisting/whitelisting guidance for each blacklist's specific process and fees.

Cloud/VPS hosts and indie SaaS founders are getting blacklisted by ASN-level policies like UCEPROTECT's without warning, usually discovering it only after emails start bouncing; a proactive monitoring and alerting tool fills the gap left by manual, after-the-fact lookups.

Demand

Developers and small businesses running mail or web servers on DigitalOcean, Linode, Vultr, and Hetzner want early warning of ASN/IP reputation problems because the current discovery path (a customer complaint or bounced email) means damage is already done by the time they notice.

• Hacker NewsNews

  Tell HN: Uceprotect is extorting website owners — 99 points, 59 comments; poster says they discovered the blacklisting by accident.

• Hacker News comments threadOpinion

  Multiple commenters share anecdotes of being blacklisted on cloud-provider IP ranges with no prior notice, discovering it only via failed email delivery.

Stack

• DNSBL/RBL lookup APIs (UCEPROTECT, Spamhaus, SORBS)
• Python or Node cron worker for scheduled checks
• Postgres for IP/ASN history
• SendGrid or Postmark for alert emails
• Twilio or Slack webhook for real-time alerts
• Simple Next.js dashboard

Solo + AI difficulty

The core RBL-query logic is easy (DNS-based lookups against known blacklist zones, well documented), and a cron-plus-alerts MVP is buildable in about a week with AI assistance; the harder parts are keeping a current, accurate list of RBL-specific delisting procedures/fees and handling false positives/rate limits from the blacklist providers themselves.

Entry threshold

Low barrier: DNSBL/RBL lookups are a well-documented, free, scriptable protocol, so a solo builder can ship a monitoring/alerting MVP (cron check plus email/Slack alert) in days; the harder part is building trust and a database of provider-level ASN reputation over time.

Window

3-6 months

Where to find first users

• r/devops and r/sysadmin
• r/selfhosted and indie hacker communities
• Hacker News Show HN launch
• DigitalOcean/Linode/Hetzner community forums

Competitors

• MXToolbox
• mail-tester.com
• multirbl.valli.pl

Counter-signals & risks

• UCEPROTECT may frame its listing policy as a legitimate anti-spam deterrent and its fees as processing/verification costs rather than extortion, which weakens the predatory-practice angle some marketing would rely on.

• Major mailbox providers like Gmail and Outlook may not weight UCEPROTECT heavily in their own filtering decisions, so being listed may have limited real-world delivery impact and reduce urgency for paid monitoring.

• Free multi-RBL checkers (MXToolbox, mail-tester, multirbl.valli.pl) already cover UCEPROTECT and other blacklists, so a new paid tool needs a clear differentiator beyond lookup — likely continuous monitoring and alerting, not one-off checks.