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Suppression Segments: The List You Should Never Mail

There is a segment on your list that costs you money every time you mail it, and the right move is to stop mailing it entirely.

A suppression segment holds the addresses you should never email: unsubscribes, hard bounces, spam complaints, and the long-unengaged. Klaviyo's rule of thumb is five or more emails received with zero opens or clicks in 90 days, and Gmail and Yahoo require spam complaints below 0.10 percent, so mailing the dead weight risks the whole list.

What goes in the suppression segment

Four kinds of address go in. Unsubscribes, which are legally required to be suppressed. Hard bounces, which will never deliver. Spam complaints, which are the addresses most likely to complain again. And the long-unengaged: subscribers who received five or more emails and opened or clicked none of them in the last 90 days, which is Klaviyo's definition of an unengaged segment. The never-engaged are worse: five or more emails in 180 days, zero opens, zero clicks, zero product views, zero orders, ever.

These are not bad people. They are people who stopped caring, or whose inbox changed, or who signed up for one discount and never came back. Mailing them does not win them back. It trains the spam filters to distrust you, and the filters do not distinguish between your good mail and your dead mail.

The sunset flow before the suppression

Suppression is the last step, not the first. Before an address goes into the suppression segment, it goes through a sunset flow: one final attempt, usually a single email asking if they still want to hear from you, with a clear way to stay. If they engage, they stay on the list. If they do not, they go into suppression, permanently.

The sunset flow is short on purpose. One email, maybe two, and then done. A long win-back sequence sent to people who have ignored you for six months is not a win-back sequence, it is spam with a nicer name, and the spam complaints it generates are the reason the suppression exists.

What suppression does and does not do

Suppression in Klaviyo prevents email marketing account-wide, which is the point: the address cannot be mailed by any campaign or flow, from any list. It does not affect SMS or push, which are separate channels with separate consent, and it does not delete the profile. The data stays, the mail stops.

Suppression is also manual in Klaviyo: it is a bulk action, not a flow action, which means someone has to do it on purpose. That friction is why so many lists never get suppressed. The fix is a monthly habit: run the unengaged definition, run the sunset flow, suppress the remainder. Thirty minutes a month, and the list gets healthier every time.

The deliverability math that forces the issue

Gmail and Yahoo's bulk sender rules require spam complaints below 0.10 percent, and never reaching 0.30 percent. A list padded with unengaged addresses pushes the complaint rate up, because the people most likely to complain are the people who do not remember signing up. A 0.30 percent complaint rate does not just hurt the campaign, it hurts the sender reputation, which hurts every campaign after it.

The math is the argument for suppression, and it is the only argument that matters to a team that does not want to shrink its list. A smaller list with a lower complaint rate delivers more mail to the inbox than a larger list with a higher one. Suppression is not losing subscribers. It is protecting the ones you kept.

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Frequently asked questions

What is an email suppression list?

A list of addresses you should never email: unsubscribes, hard bounces, spam complaints, and the long-unengaged. In Klaviyo, suppression prevents email marketing account-wide, while SMS and push are unaffected.

When should I suppress an unengaged subscriber?

After one final sunset-flow attempt. Klaviyo's rule of thumb is five or more emails received with zero opens or clicks in 90 days. If they do not engage with the sunset email, suppress them permanently.

Does suppression affect SMS and push?

No. Email suppression in Klaviyo prevents email marketing only. SMS and push are separate channels with separate consent, so a suppressed email address can still receive texts if they opted in.

What is the Gmail spam complaint limit?

Gmail and Yahoo require bulk senders to keep spam complaints below 0.10 percent, and never reach 0.30 percent. Mailing unengaged addresses pushes the rate up, which hurts sender reputation and inbox placement for every campaign.