How iBlockSpam works

The short version

iBlockSpam is an inbound email filter that works at the MX level. Your domain's MX records tell the world's mail servers where to deliver mail for your domain. When you point them at our filtering servers, every inbound message is checked for spam, viruses, malware, phishing and spoofing first. Clean mail is then delivered to your own mail server. Suspicious mail is held in quarantine, where you can review it.

Nothing about your mailboxes changes. You keep Microsoft 365, Google Workspace, cPanel/WHM, Exchange or whatever you use today.

The mail route

Step 1: Check

Start with the free Email Health Check. It reads your public DNS records (MX, SPF, DMARC and common DKIM selectors) and explains what it finds. You don't need an account or an email address.

Be aware of what a DNS check can and can't tell you:

• It can show where your MX records point and whether your SPF and DMARC records are valid.
• It can't prove that mail is filtered, or that a message was delivered.
• A DKIM selector we can't find is unknown, not broken. Selectors aren't published in a list, so we can only test common ones.

You can also use the individual tools: MX Lookup, SPF Checker, DMARC Checker and DKIM Checker.

Step 2: Configure

Configuration has two parts, and the order matters.

Prepare your mail server first

Your mail server needs to accept mail arriving from our filtering servers, and treat it correctly.

• Microsoft 365: create an inbound Partner connector and turn on Enhanced Filtering for Connectors, so Microsoft sees the original sender's IP address rather than ours. See Microsoft's guidance on Enhanced Filtering for Connectors. Full steps are on our Microsoft 365 page.
• Google Workspace: add our servers as an inbound gateway, following Google's inbound gateway instructions. See our Google Workspace page.
• cPanel/WHM: confirm how your server routes mail for the domain before changing anything. See our cPanel/WHM page.

Then change your MX records

The guided setup wizard shows your current DNS and the new values side by side, so you can see exactly what will change. It also records your old values and gives you rollback steps. We don't edit your DNS for you; you make the change at your DNS host.

Tip: lower your MX record's TTL (for example to 300 seconds) a day before the change. Mail servers cache DNS for the TTL period, so a shorter TTL makes both the switch and any rollback faster.

Step 3: Verify

Once your new MX records are visible, send a test message from an outside address to a mailbox you own. Then confirm:

1. The message arrived in the inbox.
2. Its headers show it passed through our filtering servers. Our Email Header Analyzer runs in your browser and uploads nothing.
3. It appears in your message history in the iBlockSpam portal.

If the message doesn't arrive, roll back using the steps the wizard saved, and contact support.

Step 4: Monitor

DNS changes over time. A new IT provider, a website migration or a DNS host change can quietly point your MX records somewhere else, or break SPF and DMARC. Domain monitoring checks your MX, SPF and DMARC records and alerts you when they drift.

Read more about domain monitoring, or compare plans on the pricing page.

What happens to mail every day

• Clean mail is delivered to your mail server.
• Suspected spam goes to the recipient's personal quarantine, with a digest email on the schedule you choose.
• If your mail server is down, mail is held for up to 5 days and delivered when it's back.
• Message history is kept for 30 days, so you can trace what happened to a message.

Leaving is part of the design

If you stop using iBlockSpam, you point your MX records back to your mail provider, wait for the change to propagate, and confirm mail arrives directly. Read our migration guide for the details. For the bigger picture, see why businesses choose iBlockSpam and the FAQ.