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Frequency caps by segment: the rule that stops your best buyers getting your most emails

The segment that converts best is the segment you mail most, and the segment you mail most is the one that burns out first. Caps by segment break the loop.

Your best buyers get your most emails, and your most emails go to your best buyers. That is the loop that burns a list: the segment that converts best is the segment you mail most, and the segment you mail most is the one that burns out first. Frequency caps by segment break the loop, and the cap is set by the segment, not by the calendar.

The loop that burns a list

The loop starts with a good number. A segment converts well, so it gets mailed more. It converts well again, so it gets mailed more again. Each send earns revenue, and each send also costs a little attention, a few unsubscribes, and a few spam complaints. The revenue shows up in the report. The cost shows up months later, when the segment that converted best has the highest unsubscribe rate and the lowest engagement.

The 30, 60, 90, and 180-day engagement tiers exist because of this loop. A buyer engaged in the last 30 days is not the same as one engaged 180 days ago, and mailing them at the same frequency treats them as if they were. The cap is the correction: the frequency follows the engagement, not the conversion rate.

Setting the cap by segment

Start with the engagement tier. A buyer engaged in the last 30 days can take three to five emails a week. A buyer engaged in the last 60 days can take two. A buyer at 90 days can take one. A buyer at 180 days should get one a month, and only if the content is worth it. These are starting points, not rules, and the data will move them.

Then layer the value. A VIP who buys monthly can take more mail than a one-time buyer, because the relationship supports it. A new subscriber in a welcome flow can take daily mail for a week, because they asked for it. The cap is a function of engagement and value together, and a single global cap gets both wrong.

What happens when the cap is ignored

The ignored cap shows up in three numbers. Unsubscribes rise, first in the most-mailed segment, then across the list. Spam complaints rise, because a customer who cannot find the unsubscribe link uses the spam button instead. And engagement falls, because the customers who stay stop opening, and the ones who open stop clicking.

Klaviyo's benchmarks say segmented campaigns earn 46 percent higher opens and 101 percent higher clicks than unsegmented ones. Those numbers assume the segment is healthy. A segment mailed past its cap is not healthy, and the benchmarks do not apply to it.

The cap as a segment rule, not a campaign rule

Set the cap in the segment, not in the campaign. A campaign-level cap is a promise the next campaign breaks. A segment-level cap is a rule every campaign inherits, and it is the only way the cap survives a busy quarter. When a campaign wants to mail a segment past its cap, the answer is a decision, not an accident: raise the cap and record why, or mail a different segment.

Review the caps quarterly, with the segments. A cap that never changes is a cap that is never tested, and an untested cap is a guess with a rule attached to it.

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Frequently asked questions

What is a frequency cap by segment?

A frequency cap is a limit on how many emails a person in a segment receives in a period. A cap by segment sets that limit per segment, so your best buyers get fewer emails than your window shoppers, or more, depending on what the data says. The cap is a rule, not a guess.

Why cap by segment instead of one cap for the whole list?

Because a single global cap is wrong for everyone. A daily cap of one email is too many for a lapsed buyer and too few for a new subscriber in a welcome flow. Caps by segment match the frequency to the relationship, and the relationship is different for every segment.

How do I know if a cap is too high or too low?

Watch unsubscribes and spam complaints per segment, not opens. A segment whose unsubscribes rise after the third email in a week is telling you the cap is too high. A segment whose unsubscribes stay flat at five emails a week is telling you the cap can rise.

How many emails a week is too many?

It depends on the segment. A new subscriber in a welcome flow can take daily mail for a week. A lapsed buyer should get one email a month, at most. A VIP can take more, because they asked for it. The number follows the relationship, not the calendar.