Suppression Segments: The People You Should Never Email Again
Suppression is not punishment. It is protection. A suppression list is a firewall between the sender and deliverability disaster, and the senders who treat it as a junk drawer are the ones who end up in spam.
A suppression list is a database of contacts you have chosen not to email, either permanently or temporarily: unsubscribers, hard and repeated soft bounces, spam complainers, and inactive users. The process for deliverability has three steps. Create a segment of unengaged contacts, exclude that segment from sends, and suppress the never-engaged segment. An unengaged contact is someone who received at least five emails and opened none of them in the last 90 days. A never-engaged contact received at least five in the last 180 days and never opened or clicked. Suppress them after one final re-engagement attempt through a sunset flow.
Exclusion is a pause, suppression is a decision
Exclusion and suppression are different tools, and confusing them is how lists get damaged. Exclusion removes a segment from a specific campaign, which is a pause: the contacts stay in the account, they stay eligible for flows, and they can come back. Suppression prevents profiles from receiving email marketing across the whole account, which is a decision: the contacts stay in the database, but they do not get campaigns. Suppression does not suppress SMS or push notifications, which are separate channels with separate consent, and that distinction matters when a contact unsubscribes from email but still wants texts.
The bulk action applies to the segment's current members, and profiles who join later are not automatically suppressed, which is the detail that catches teams. Suppressing the never-engaged segment today does not suppress the profiles who become never-engaged next month. The suppression has to be repeated, or automated, and the segment has to be rebuilt on a schedule. A suppression list that is not maintained is a list that quietly refills with the same people it was built to exclude.
Related reading on this site: SegmentMuse and Predictive Segments: When a Model Score Beats Your RFM Buckets cover the neighbouring problems in more depth.
The three steps, and the sunset flow between them
Klaviyo's list cleaning process has three steps, and the order matters. First, create a segment of unengaged contacts: profiles who received at least five emails over all time and opened none of them in the last 90 days. Second, exclude that segment from the majority of campaigns, because continuing to send to people who do not open or click damages deliverability. Third, suppress the never-engaged segment: profiles who received at least five emails in the last 180 days and never engaged at all. Before suppressing, send one final re-engagement attempt through a sunset flow, and wait until profiles have completed it without engaging.
The sunset flow is the last chance, and it should be honest about it. One email, or a short series, asking whether the subscriber still wants to hear from the store, with a clear action to stay. The subscribers who engage earn their spot back. The ones who do not are suppressed, and the list gets smaller and healthier in the same week. Unengaged contacts who have not been suppressed may still receive occasional high-priority messages, such as abandoned cart flows or re-engagement messages, if the sender chooses not to exclude them from those sends, but the regular campaigns stop, and that is the point.
What the mailbox providers are actually watching
Mailbox providers watch engagement, not headcount, and the signals they weigh are recent. Validity's guidance lists the three they check: recent opt-ins, whether the contact gave explicit consent recently; recent purchases within 120 days; and recent opens and clicks within 120 days. If the answer to all three is no, the contact should be cut loose. Contacts that have not engaged in three to six months should be removed, and if a contact has not responded in over a year, the address may have been recycled into a spam trap, which is a deliverability event, not a metric problem.
Gmail now prompts subscribers to opt out of an email program after 30 days of inactivity, which is the mailbox provider doing the suppression for the sender. A spam complaint rate above 0.1 percent can seriously damage deliverability, and a list that keeps mailing the unengaged will cross that line on a bad week. The suppression segment is the sender's answer to that pressure: a standing list of the people who should never be emailed again, maintained monthly, audited quarterly, and respected by every campaign. A sender who treats suppression as a chore will keep paying for it in the inbox. A sender who treats it as a firewall will stop paying at all.
Frequently asked questions
What is a suppression list?
It is a database of contacts you have chosen not to email, either permanently or temporarily: unsubscribers, hard and repeated soft bounces, spam complainers, and inactive users. Suppression is protection, not punishment, and it keeps risky contacts from harming sender reputation.
What is the difference between excluding and suppressing a segment?
Exclusion removes a segment from a specific campaign, which is a pause. Suppression prevents profiles from receiving email marketing across the whole account, which is a decision. Suppression does not affect SMS or push notifications.
How do I identify unengaged contacts to suppress?
Create a segment of profiles who received at least five emails and opened none in the last 90 days, exclude them from campaigns, and suppress the never-engaged segment, who received at least five in 180 days and never engaged, after one final re-engagement attempt.
Does suppressing a segment cover people who join it later?
No. The bulk suppression action applies to the segment's current members only, and profiles who join later are not automatically suppressed. The suppression has to be repeated or automated on a schedule.