Why your email list isn't growing, and where it leaks

Your email list isn't growing because it leaks at one of three stages: acquisition (not enough people sign up), conversion (subscribers never place a first order), or retention (people unsubscribe, bounce or stop buying as fast as new ones arrive). Diagnose which stage leaks before you change anything. A new pop-up fixes nothing if the leak is in retention.

This guide gives you the numbers to pull, a simple decision rule for each stage, and the exact Claude prompt to run the diagnosis. It also covers the case most people miss: a list that grows in size but not in revenue. That is a leak too.

01Why your email list isn't growing: the three leaks

Every subscriber passes through three stages. Each one can leak on its own, and each needs a different fix.

Most advice on growing a list is acquisition advice: more pop-ups, bigger discounts, more lead magnets. That only helps when acquisition is the leak. If your problem is retention, more sign-ups just pour more water into a leaking bucket.

02Measure net growth before list size

List size tells you how many profiles you have collected. Net growth tells you whether the list is actually growing. Work it out per month:

Net growth = new sign-ups - unsubscribes - hard bounces - spam complaints
Net growth rate = net growth / list size at the start of the month

An example with made-up numbers: you start the month at 20,000 profiles, gain 900 sign-ups, and lose 300 to unsubscribes, 80 to bounces and 20 to complaints. Net growth is 500, a net growth rate of 2.5%. A dashboard showing 900 new profiles overstates your growth by 400.

What counts as a good rate? The honest answer: published benchmarks for monthly list growth disagree widely. Agency and vendor pages quote different ranges, and some label their figure an industry estimate rather than measured data. Treat any benchmark as a rough sanity check at most. The comparison that matters is against your own last three to six months.

03The numbers to pull for an email list audit

You don't need a full audit to find the leak. A typical ecommerce email audit, as Top Growth Marketing describes it, covers deliverability, list health, flow performance, campaign metrics and revenue attribution. The Commerce Shop's audit outline puts list growth and subscriber retention inside the same list analysis, which is the right instinct: they are two sides of one number.

For a list that isn't growing, start with the narrower set below. Pull 90 days, split by month, so you can see a trend.

Also note your list size and average order value. They let the diagnosis put the leak in money terms instead of percentages.

04Decision rules for each stage

Compare each number against your own previous months. Then use these rules.

Acquisition leaks if sign-ups per 1,000 sessions fell while traffic held, or if one source brings almost all your sign-ups and the rest bring close to none. Check the pop-up first: the offer, the timing, and how it behaves on mobile. That is vendor content, so treat it as a loose reference only.

Conversion leaks if sign-ups are steady or rising but the share of new subscribers who place a first order within 30 days is falling. Look at the welcome flow: does the first email deliver what the pop-up promised, and does each email give a reason to buy? Then look at which sources the non-buyers came from. A giveaway entry form can fill a list with people who never planned to buy.

Retention leaks if unsubscribes, complaints or bounces per campaign are trending up, or if net growth is falling while gross sign-ups hold. Check send frequency, which campaigns spike unsubscribes, and whether old, unengaged profiles still get every send.

If two stages look bad, start with the one that loses the most subscribers or the most money per month. Fix one stage at a time, or you won't know what worked.

05The prompt

You can run this method by hand with a spreadsheet, or with Claude. The prompt below uses the /margarita‑list‑growth skill, which diagnoses whether your list leaks at acquisition, conversion or retention and returns targeted fixes for that stage. It costs $2. Without the skill, delete the first line and paste the rest. Claude will still follow the structure; you just give it more of the method yourself.

Use /margarita-list-growth. Attached are my signups for the last [90] days by source, my popup and its offer, my welcome flow, and unsubscribe and complaint rates per campaign. List size: [SIZE]. Average order value: [AOV].

1. Say which stage leaks most: acquisition, conversion, or retention. Show the numbers that point to it.
2. List up to five fixes for that stage. For each: what to change, the evidence, and effort (S, M, or L).
3. Name one thing I should stop doing.

Use only the numbers I attached. If you need a number I did not give you, name it instead of guessing.

Attach real exports. Summaries typed from memory hide the numbers that matter. The last instruction matters most: it stops Claude from filling a gap with a guess that looks like data.

06How to check the output

1. Recalculate the rate the diagnosis rests on. If it says conversion leaks because few new subscribers bought, divide the two numbers yourself.
2. Check the same leak in a second month. One bad month can be a promotion, a holiday or a tracking glitch. Two in a row is a pattern.
3. Change one thing at a time. If you swap the pop-up offer and rewrite the welcome flow in the same week, you won't know which one moved the number.
4. Write down the before numbers. Net growth, the rate behind the diagnosis, and revenue per subscriber. Measure again in 30 days.
5. Reject any fix that cites a number you did not give it. The prompt asks Claude to name missing data instead of guessing. If it guessed anyway, send it back.

07After the diagnosis: where to go next

The diagnosis tells you where to work. What you do next depends on the stage.

• Acquisition leak: test one change to the pop-up offer or timing, and keep everything else fixed for 30 days.
• Conversion leak: rebuild the welcome series. The Klaviyo welcome flow guide walks through a 3 to 7 email sequence with routing by segment.
• Retention leak: check what you send before you send more. The pre-send email QA checklist catches fake urgency, missing footers and other things that give people a reason to unsubscribe or complain.

This is workflow 1 of 6 in the series. The Claude for email marketing guide shows all six in order.

08Quick answers

How do I calculate my email list growth rate?

Take new sign-ups for the month, subtract unsubscribes, hard bounces and spam complaints, and divide by your list size at the start of the month. That is your net growth rate. Gross sign-ups alone overstate growth.

What is a good monthly list growth rate for ecommerce?

Published benchmarks disagree widely, and some are labeled estimates rather than measured data. Use them as a rough range at most and compare against your own last three to six months instead.

Why is my list growing but my email revenue is not?

That points to a conversion or retention leak. Check how many new subscribers place a first order within 30 days and whether revenue per subscriber is falling month over month.

Do I need the /margarita‑list‑growth skill to do this?

No. The method works with a spreadsheet and the prompt in this guide. The $2 skill gives Claude the diagnosis structure so it returns the leaking stage and targeted fixes for it.

How long before I know a fix worked?

Write down the before numbers and measure again in 30 days. Check the same metric in a second month before you call it a win or a loss.