Email list hygiene checklist

List hygiene is a cadence, not an event. Once a quarter: suppress everything that hard-bounced, dedupe the remainder, re-check domains, sunset long-term non-openers, and record the counts so you can tell whether the list is improving.

Twenty minutes of that is worth more than any subject-line test, because it changes the denominator every rate is calculated against.

The checklist

Suppress hard bounces permanently. Not for one campaign — forever. Add them to a suppression list that survives every import.
Honour complaints immediately. A complaint is a request to never hear from you again, and it is the metric Google publishes guidance on.
Dedupe on the canonical address. Case, plus-tags, Gmail dots. Keep the earliest consent date and the newest engagement.
Repair typos, then check MX. Drop every address on a domain with no mail server; that is a guaranteed bounce you can remove for free.
Flag role and disposable addresses out of nurture audiences.
Sunset non-openers. No opens in six months, no clicks in twelve — move them to a re-permission campaign, then drop them if they stay silent.
Record the numbers. Rows in, rows after dedupe, rows after domain checks, bounces and complaints per send.

Why sunsetting is the part people skip

An unengaged address is not neutral. It lowers your open rate, which lowers how much providers trust your mail for everyone else on the list, and some of those addresses have been recycled into spam traps. Removing people who never open feels like shrinking your audience; it is actually raising the value of the ones who remain.

Metrics worth tracking per send

Hard bounce rate (target: as close to zero as you can measure)
Complaint rate (Google's published guidance: below 0.3%, measured in Postmaster Tools)
Unsubscribe rate
Delivered vs sent — the gap is where filtering hides

Doing the whole thing in one pass

Paste the export into a browser tool, run dedupe and domain checks together, export the cleaned CSV and the full report. Keep the report: it is your record of what you removed and why, which is the difference between hygiene and unexplained data loss.

Check your own list in about 30 seconds. Paste or drop a CSV — duplicates, typos, role addresses and dead domains, all handled in your browser. Free for the first 100 addresses, $19 once for unlimited.

Open the tool

Common questions

How often should I clean?

Quarterly for a stable list, and always before a large send or after importing anything from a third party. Cleaning immediately after an import catches the problems while you still remember where the data came from.

Does removing non-openers hurt revenue?

Usually the opposite. Apple's Mail Privacy Protection prefetches images, which inflates opens for some segments and hides them for others — so treat opens as a rough signal and use clicks as the stronger one before deleting anyone.

Last updated 2026-10-23.