Email List Hygiene: Email List Hygiene: Clean Your List and Protect Your Sender Reputation
Why list hygiene is the most underrated factor in deliverability — and a step-by-step process for cleaning your contact database.
The 4 types of harmful addresses
Hard bounces: remove immediately. These are invalid email addresses that will never deliver. Sending to hard bounces repeatedly signals to inbox providers that you're not maintaining your list — and they'll start filtering your emails to spam.
Soft bounces: suppress after 3 consecutive failures. Soft bounces are temporary — full mailboxes, temporary server issues, or auto-responders. After 3 consecutive failures over 7-10 days, treat the address as invalid.
Spam traps: addresses maintained by blacklist operators to catch bulk senders. You can't identify them by looking at them — they look like real email addresses. The only way to avoid them is to never send to lists you haven't verified.
Complaints: suppress immediately. When someone marks your email as spam, never send to them again. Even one complaint after suppression can trigger sending limits from inbox providers. Purchased lists contain all four types in high concentrations.
The list cleaning process
Run through an email verification tool before every major campaign. Tools like ZeroBounce, NeverBounce, and MillionVerifier identify invalid addresses, disposable domains, and known spam traps. This takes minutes and saves your sender reputation.
Remove invalid, disposable, and role-based addresses (info@, admin@, support@). Role-based addresses have low engagement rates and high complaint rates — they're not real people, they're shared inboxes.
Segment by last engagement date. Contacts with no opens in 90+ days should receive a re-engagement campaign before your next broadcast. Contacts with no opens in 180+ days should be suppressed outright — they're dragging down your deliverability.
Running a re-engagement campaign
Send 2-3 emails with a clear subject: 'Are we still a good fit?' or 'Last chance to stay on our list'. Make unsubscribing easy and obvious — the goal is to identify who still wants to hear from you.
Offer an incentive to re-engage: a discount, exclusive content, or early access to a new feature. If they don't open or click after 2-3 attempts, they're not interested — suppress them.
After the sequence, suppress all non-openers. Your list will be smaller but deliverability, open rates, and revenue per contact will all increase. A 10,000-contact list with 40% open rates outperforms a 50,000-contact list with 15% open rates.
How often to clean your list
Run email verification before every major campaign — at minimum monthly for active senders. If you send daily, verify weekly. The cost of verification ($5-20 per 10,000 contacts) is negligible compared to the cost of a burned domain.
Set up automated suppression rules in your CRM: suppress anyone who hasn't opened in 90+ days, anyone who hard bounces, and anyone who marks you as spam. SpaceCRM handles this automatically with its built-in deliverability monitoring.
Track your list health metrics: bounce rate (target: under 2%), complaint rate (target: under 0.1%), and engagement rate (target: 20%+ opens). If any metric deteriorates, run a full list verification immediately.