What makes an address “to monitor” instead of “to suppress”?
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When you run a list through validation, you'll get back addresses that can't be cleanly classified as either "definitely valid" or "definitely invalid." These live in a gray zone: technically reachable but carrying some level of uncertainty or early warning signals. These are your "to monitor" addresses.
An address belongs in the monitor category when it has a potential problem but no confirmed harm yet:
- Catch-all domains: The server accepts everything during validation, so you can't confirm whether this specific inbox actually exists. It might work fine. It might bounce on delivery. Watch it across a couple of sends before making a suppression call.
- Inconsistent engagement: The address delivered and opened previously, but hasn't engaged in a while. Not long enough to suppress, but worth tracking. If engagement doesn't resume, this moves toward suppression territory.
- Soft bounce patterns: The address is bouncing temporarily but hasn't crossed into repeated hard-bounce territory. Monitor the pattern. Three or more soft bounces with no successful delivery is typically when monitoring tips into suppression.
- New acquisition from a borderline source: An address from a partner co-registration or a giveaway campaign that looked legitimate but carries higher-than-normal risk signals. Send once, observe, then decide.
The difference from suppression: suppressed addresses should never receive mail from you again. Monitored addresses can still receive mail, but they're flagged for review. You're watching for the pattern that confirms whether to keep them active or suppress them.
The difference from "to keep": addresses you'd confidently send to without any caveats. Clean acquisition, valid status, positive engagement history.
A practical way to handle monitor-tier addresses: segment them separately and send less frequently, or wait until they've shown engagement on a re-engagement campaign. If they engage, move them to active. If they bounce or continue not engaging, suppress them based on your policy threshold.
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