Klaviyo List Hygiene Agent

Bounces are the cheapest warning a sender ever gets, and most lists only act on them after a campaign has already gone badly. This agent reads each one as it fires, suppresses the profiles your rules say to suppress, writes the bounce type and date onto the profile so the decision is legible, and watches the account rate so a spike reaches you mid send rather than in next month's review. Nothing it does is permanent, which is the whole design: a suppression lifts in a click, so it never needs the power to delete anyone.

What people use it for

• Catch a bad signup source - A run of dead addresses arriving from one form or one giveaway shows up as a rate movement instead of thirty separate cleanups. You learn the source is poisoned while you can still switch it off.
• Suppress without losing history - A suppressed profile keeps its orders, its opens and its properties, with the bounce reason and date sitting on it. Support can still answer questions about that customer, and you can lift the suppression yourself.
• See a spike during the send - The bounce rate is measured against the recent baseline on every single bounce, so a campaign going wrong reaches the channel while it is still sending.
• Treat a full mailbox as temporary - Soft failures are counted, not punished, until they reach the streak your rules describe. Nobody loses a paying customer because their inbox was full for three days while they were away.

Before you fork

What do I have to connect?

One Klaviyo account with API access to profiles, suppressions and metrics, plus the Slack channel that should hear about spikes. Then you write the hygiene rules: which bounces earn a suppression, the number of soft failures that add up to a streak, the profile property that records the reason, and the rate you consider abnormal. Nothing runs until a bounce actually fires.

Could it suppress someone it should not have?

Yes, and that is exactly why suppression is where its power stops. A suppressed profile keeps everything, and you can lift it in Klaviyo in seconds. Deleting and unsubscribing are not available to it at all, so its worst possible mistake is one you can undo in under a minute. Try it against the staged bounces before anything live is connected, and check which ones it decides to touch.

What does it cost when a send goes badly?

It runs once per bounce, so a clean list barely registers and a bad send is expensive in proportion to how bad it was. A 100,000 address campaign bouncing at half a percent is 500 short runs. If that figure looks alarming, it is the same figure that was already burning your domain reputation, only now visible on the day it happens.