How to protect remaining healthy IPs or subdomains?

When one of your IPs or domains is in trouble, the instinct is to focus entirely on fixing the broken thing. But the smarter move is to also protect the assets that are still healthy. Reputation contamination is real, and if you're not careful, a struggling marketing IP can drag down a clean transactional one sitting next to it in the same subnet.

Here's what actually matters when you're trying to keep healthy infrastructure healthy during a crisis.

Keep traffic strictly separated

Don't let any traffic from a problem segment touch a healthy IP or domain. This sounds obvious, but routing rules can get sloppy under pressure. Check your sending configuration and confirm that your affected streams aren't falling back to healthy IPs if something fails. A fallback route that quietly bypasses your separation is one of the most common ways contamination spreads.

Also watch your domain separation. Mixing a struggling marketing domain with a clean transactional domain on the same IPs is a fast track to collateral damage.

Understand the subnet risk

If your healthy and affected IPs share a /24 subnet (meaning their first three octets match, like 192.168.1.x), some spam filters and blocklists treat the whole block with suspicion. This isn't universal, but it's a real risk. If you're on a shared infrastructure provider and you don't control which subnet your IPs come from, this is worth flagging to your ESP or hosting provider now, before the problem gets worse.

Hard separation means different IPs on different subnets. Soft separation (same subnet, different headers or subdomains) offers less protection than you might think during an active reputation crisis.

Actively monitor your healthy assets

Don't just assume your clean infrastructure is still clean. Check your Google Postmaster Tools daily. Watch your domain reputation and IP reputation scores. Set up alerts so a sudden drop doesn't go unnoticed for 48 hours while you're focused on the recovery effort elsewhere.

Still if you haven't set alerts up yet, do it today. You want to know the moment something starts trending in the wrong direction, not after it's already a problem.

Reduce volume on healthy streams too

Even streams that are performing well should dial back volume temporarily during a crisis. Focus only on your highest-quality, most engaged segments. Skip anything experimental. The goal isn't to grow right now. It's to come through the crisis with as much infrastructure intact as possible.

Think of it like a precautionary slow-down. You're not pausing because healthy streams are broken. You're slowing down because low engagement on any stream can tip inbox providers toward skepticism across your whole sending footprint.

Have a reroute plan ready

And if a healthy IP starts showing signs of contamination, you need to know immediately how to reroute that traffic. Having a backup sending path ready before you need it means you're making a calm, pre-planned decision instead of a panicked one. Document which IPs and domains handle which streams, so anyone on your team can reroute quickly if you're not available.

If you're not sure how badly your current reputation has spread or whether your healthy assets are still actually clean, our free Blocklist Checker is a quick first look. And if this is actively breaking things right now, the SOS hotline is free and we actually pick up.