Email list cleaning: what to remove and when

How it works

Cleaning happens at three moments:

• As things happen. Hard bounces and spam complaints should come off the list the moment your sending provider reports them.
• On a schedule. People who have stopped engaging get a last-chance email asking whether they still want your mail. Those who stay silent are unsubscribed.
• When you import. A list moving from another platform brings its opt-outs with it. Stale or uncertain-consent addresses stay out of the active list.

Cleaning means suppressing, not deleting. Keep the record that an address must not be mailed. Delete it and the next import or signup brings it back as a fresh subscriber.

Why it matters

• Gmail recommends it. Google's sender guidelines suggest unsubscribing recipients who have multiple bounced messages, and those who don't open or read your messages.
• Fewer complaints. People who forgot about you are the likeliest to press "Report spam".
• Truer numbers. Open and click rates measured on people who read your mail tell you something.

How Mimeo handles it

The automatic part is built in. Hard bounces, spam complaints and provider-side suppressions suppress the person as soon as the webhook arrives.

For the scheduled part, a flow on the inactivity trigger sends a "still want these?" email, waits, then a prune step unsubscribes anyone who still hasn't opened or clicked. Their record shows the reason inactive, and a pruned event keeps leaving for inactivity apart from leaving by choice. An open or click since entering the flow saves them.

Unsubscribed people stay on the books, so nothing automated mails them and a later CSV import can't make them mailable again. When you migrate, import suppressions first and trim before you import. See Mimeo terms for pruning in Mimeo's own words.