List hygiene

Definition

List hygiene is the ongoing practice of cleaning your subscriber list: identifying contacts who haven’t engaged in a defined period, who have hard-bounced, who have filed spam complaints, or who have unsubscribed — and removing or suppressing them from future sends.

The practice became critical in 2026 for two reasons:

  1. Cost: Per-contact platforms (Mailchimp, Klaviyo, ActiveCampaign) bill based on active contacts. A list of 10,000 subscribers where 4,000 haven’t opened in 18 months still costs money on those platforms.
  2. Deliverability: High proportions of unengaged contacts drag down sender reputation by reducing open rates, click rates, and increasing the relative proportion of spam complaints.

Concrete example

A nonprofit has 8,000 donors in Mailchimp. 3,000 of those haven’t opened an email in two years. On Mailchimp Standard, they pay for 8,000 contacts ($115/mo in 2026). After a list hygiene pass — running a re-engagement campaign then suppressing non-responders — they’re at 5,500 active contacts. Monthly bill: $80/mo. Annual saving: $420.

The deliverability benefit is separate: the 5,500-contact list now has an open rate of 28% (up from 19%) because dormant contacts no longer dilute the metric. This improved reputation increases inbox placement rate.

The standard hygiene workflow

  1. Identify dormant contacts: Filter for contacts with no opens and no clicks in 90/180/365 days (your threshold depends on send frequency — use 90 days if you send weekly, 180 days if monthly).
  2. Run a re-engagement campaign: Send 1–2 “still interested?” emails with a strong subject line (“Are we breaking up?”, “One click to stay on the list”). Give subscribers a clear way to confirm they want to stay.
  3. Suppress non-responders: Contacts who don’t respond to the re-engagement sequence within 2 weeks → add to suppression list.
  4. Maintain a suppression list: Never re-add suppressed contacts without explicit re-consent. Hard bounces and spam complaints → permanent suppression.
  5. Repeat quarterly: Set a recurring calendar reminder. List hygiene is ongoing, not a one-off.

Platform-specific billing implications

Klaviyo: Active-profile billing (introduced February 2025) is the most aggressive — any contact emailed in the past 365 days counts. A win-back campaign that reactivates 500 dormant contacts can push you into the next billing tier. Run hygiene before any re-engagement campaign.

Mailchimp: Bills on “active” contacts (received at least one email in the past 30 days). Archive dormant contacts monthly to reduce the count.

Brevo: Per-send pricing means list hygiene matters less for cost (you’re billed on sends, not contacts). However, it matters for deliverability — sending to 8K contacts when 3K are dormant still hurts your spam complaint rate.

MailerLite: Bills on total subscriber count including inactive. Archive or delete unengaged contacts quarterly.

Automated hygiene: sunset policies

A sunset policy is an automated version of list hygiene — configure the platform to automatically suppress any contact who hasn’t opened or clicked in a defined period (typically 90–180 days). Klaviyo, ActiveCampaign, and GetResponse all support automated sunset policies.

Setting up a sunset policy removes the manual quarterly effort: contacts who don’t engage are suppressed automatically, keeping your list clean continuously.

→ Take the decision wizard to find platforms that offer automated sunset policies at your price tier.

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