The True Cost of Spam: Why Your Mail Server Is the Wrong Place to Fight It
When you measure the full cost — storage, bandwidth, IT hours, and lost productivity — the numbers tell a different story.
Indition Spam Killer sits between the internet and your mail server, filtering out spam, phishing, and malicious email in real time. No software to install. No mailboxes to migrate. Just point your MX records and you're protected.
Multi-layered detection that adapts to new threats automatically.
Every message is scored by a Bayesian classifier, 20+ heuristic rules, and authentication checks. The weighted composite score determines spam with surgical precision.
Authenticate every sender with SPF and DKIM checks. Configure per-domain policies: reject failures outright, add scoring weight, or mark as spam immediately.
Every domain gets its own upstream server, SPF/DKIM policy, greylisting rules, and spam thresholds. One account, unlimited domains, each tuned independently.
Messages are analyzed and forwarded in milliseconds. Multi-threaded architecture handles hundreds of concurrent connections without breaking a sweat.
First-time sender/IP/recipient combinations are deferred. Legitimate servers retry automatically; spambots don't. Configurable per-domain with custom defer times.
Block known bad actors by IP address, CIDR range, or sender domain. Whitelist trusted partners to bypass all checks entirely.
Real-time dashboards show message volume, spam rates, top sender domains, and per-domain breakdowns. Prometheus metrics and Grafana dashboards included.
The Bayesian classifier learns what spam looks like for your organization. Train it with your own spam and legitimate email, and accuracy improves over time.
Automatic per-IP rate limiting prevents abuse. Set thresholds per minute and per hour to stop volumetric attacks before they overwhelm your server.
Not all bulk mail is spam. Messages are classified as [SPAM], [SOCIAL], or [PROMOTION] based on authentication signals and content indicators. Your inbox stays organized.
Emails from LinkedIn, Facebook, GitHub and other social platforms are auto-tagged [SOCIAL]. Newsletters with List-Unsubscribe from authenticated senders get [PROMOTION].
Pattern matching catches what classifiers miss.
No software to install. No mailboxes to migrate. Three steps to protected email.
Update your domain's MX records to route inbound email through Spam Killer. We provide the records; you paste them into your DNS provider.
; Replace existing MX records with:
@ IN MX 10 mx1.spamkiller.online.
@ IN MX 20 mx2.spamkiller.online.
Tell us where to deliver clean email. Point to your existing mail server by IP or hostname. Support for TLS, authentication, and custom ports.
# Your domain configuration
yourdomain.com:
upstream:
host: "mail.yourdomain.com"
port: 25
use_tls: true
Configure SPF/DKIM enforcement, greylisting, spam thresholds, blacklists, and whitelists per domain. Every domain can have its own rules.
# Per-domain policy overrides
yourdomain.com:
spf:
required: true
failure_action: "reject"
greylisting:
enabled: true
defer_minutes: 2
Global defaults keep things simple. Per-domain overrides give you precision.
Built-in Grafana dashboards and Prometheus metrics give you full visibility.
All plans include every feature. You only pay for volume.
For small businesses and startups
For growing companies
For large organizations
Spam Killer acts as an SMTP proxy. You update your MX records to point to our servers. We receive inbound email, analyze it for spam, tag or reject bad messages, and forward clean email to your existing mail server. Your mail server setup doesn't change at all — we just sit in front of it.
Any mail server that accepts SMTP delivery. Exchange, Postfix, Dovecot, Zimbra, hMailServer, Google Workspace, Microsoft 365 — if it has an IP address and accepts email on a port, Spam Killer works with it.
Most customers are fully configured in under 10 minutes. The only change on your end is updating MX records (which propagate in minutes to hours depending on your DNS provider) and optionally restricting your mail server to only accept connections from our IP ranges.
Yes. Every domain can have its own upstream server, SPF/DKIM policy, greylisting settings, and more. Global defaults keep configuration simple for most domains, and per-domain overrides let you fine-tune where needed.
We run redundant MX servers (mx1 and mx2) across separate infrastructure. If one goes down, the other continues processing. And because SMTP has built-in retry logic, even if both were briefly unavailable, sending servers would retry delivery for up to 5 days. Your email won't be lost.
Typical processing time is under 50 milliseconds per message. The only intentional delay is greylisting (if you enable it), which defers first-time senders for a configurable number of minutes. Legitimate servers retry automatically.
Messages are intelligently classified into four categories. Spam gets [SPAM] in the subject line. Social media notifications (LinkedIn, Facebook, GitHub, etc.) are tagged [SOCIAL]. Legitimate marketing emails with proper authentication are tagged [PROMOTION]. Clean personal email passes through unmodified. Every message also gets X-Spam-Status, X-Spam-Score, and X-Spam-Classification headers for easy filtering in your mail client or server rules.
Yes. The Bayesian classifier can be trained with your own spam and legitimate email via our training interface. The more data you feed it, the more accurate it becomes for your specific email patterns. It activates after 50 training samples.
When a message scores as spam but comes from an authenticated sender (SPF pass + DKIM pass), we check two things. First, is it from a known social platform (LinkedIn, Facebook, GitHub, etc.)? If so, it's tagged [SOCIAL] instead of [SPAM]. Second, does it have promotional indicators (List-Unsubscribe header, marketing sender patterns, known marketing platforms) and a valid MX record? If so, it's tagged [PROMOTION]. You can customize the social domain list, marketing sender patterns, and mailer lists in your config. The feature can be disabled entirely if you prefer pure spam/ham classification.
Email security insights, practical how-tos, and the business case for doing spam right.
When you measure the full cost — storage, bandwidth, IT hours, and lost productivity — the numbers tell a different story.
Email authentication standards are the foundation of a spam-free inbox. Here's what each one does and how they work together.
Greylisting works because spambots don't play by the rules. Legitimate mail servers retry. Most spammers don't.
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Free for 14 days. Cancel anytime. We'll help you set up your MX records.