Building Your List

The foundation of email marketing is your list. Not the size of it, but the quality. A list of 2,000 people who genuinely want to hear from you will outperform 20,000 unengaged contacts every single day.

I’ve watched this play out hundreds of times across SmartrMail customers. One brand cuts their list from 80,000 to 25,000 by removing everyone who hasn’t engaged in six months. Their revenue goes up 40%. It feels counterintuitive. It works every time.

The vanity of a large list number is one of the hardest things to let go of in email marketing. But every unengaged subscriber costs you money in two ways: you pay your ESP for them (most charge by subscriber count), and their lack of engagement drags down your sender reputation, which reduces inbox placement for the subscribers who actually want your emails. A smaller, engaged list is cheaper to maintain and more profitable to send to.

Sixty-six percent of consumers have made a purchase as a direct result of an email marketing message. But only when they actually wanted to receive it. The quality of your list determines the quality of your results. Everything in this chapter is about building that quality from the start and maintaining it over time.

Organic Growth Strategies

Lead magnets. The data is pretty clear: offering something valuable in exchange for an email address works. Offering a free template increased email signups by 384% in one study. Free samples can achieve conversion rates of up to 5.2%. Offering a gift or a chance to win can increase signups by 300%.

The best lead magnets share three qualities: they’re immediately available, they address a specific need, and they can be consumed in minutes. A checklist, template, or calculator beats a 60-page PDF every time. IndieHackers members consistently report that the fastest lead magnets to create (a one-page checklist or template) convert better than elaborate ebooks or courses. The value is in specificity and immediacy, not comprehensiveness.

As Nathan Barry (founder of Kit, formerly ConvertKit) has demonstrated with his own audience building, the lead magnet needs to solve one specific problem for one specific person. “Get better at marketing” is weak. “Get 3 email templates every week” is strong.

Content upgrades. Using different lead magnets for specific posts yields far better results than one generic lead magnet across your entire site. Content upgrades have been reported to increase opt-in rates by 5-10x compared to generic sidebar signup forms. If someone’s reading about abandoned cart recovery, offer them an abandoned cart email template, not a generic “email marketing guide.” Match the offer to the content.

Signup forms. Using a form instead of a link can increase opt-in rates by 20-50%. The optimum number of fields is between 3-5 for top-of-funnel assets, though starting with email only and testing additional fields later is the smarter play. Using enticing button copy can lift opt-in rates by 33.1%. “Get my templates” outperforms “Subscribe” every time.

Liz Wilcox, who built a community of over 4,000 email marketing enthusiasts, advocates for making your signup promise specific and achievable rather than vague. Specificity is the single biggest lever for signup conversion.

What’s working in 2025-2026 for lead magnets:

• Templates and swipe files convert highest with lowest effort to consume. Email templates, spreadsheet templates, Notion templates, Canva templates. People want something they can use immediately.
• Checklists and cheat sheets. One-page actionable guides for specific tasks. Quick to create, quick to consume.
• Calculators and tools. ROI calculators, pricing tools, grading tools. These take more effort to build but have high perceived value and strong conversion rates.
• Mini-courses delivered by email. A 3-5 day email course teaching one specific skill. These double as your lead magnet and the beginning of your nurture sequence.
• Quizzes. “What type of [X] are you?” followed by email capture for results. Interact and Typeform make these straightforward. High completion rates because curiosity drives people to finish.

What’s declining: long PDFs and ebooks that people download and never read, generic ‘ultimate guides’, and webinar registrations (unless very specific and timely).

The Popup Debate

Popups are controversial. Designers hate them. Marketers love them. The data is pretty clearly on the marketers’ side.

Well-timed popups convert at 3-5% of visitors. The top 10% of popups convert at 9.28%, according to Sumo’s data. A generic “subscribe to our newsletter” with no delay converts under 0.5%. The difference is timing, offer, and design.

Exit-intent popups fire when the cursor moves toward closing the tab. Conversion rates of 4-7%. These catch people who were leaving anyway, so there’s minimal disruption to the browsing experience.

Timed popups fire after 15-30 seconds on the page. Conversion rates of 2-4%. The delay matters. Firing immediately (zero-second popup) is annoying and converts under 1%. Fifteen seconds lets someone start reading before you interrupt.

Scroll-triggered popups fire when someone scrolls 50% or more down the page. Conversion rates of 2-5%. These target people who are actively engaged with your content.

Two-step popups ask a question first (‘Want 10% off your first order?’) with a yes/no choice, then show the email field only after someone clicks yes. These consistently outperform single-step forms by 30-50%, because the initial commitment makes people more likely to follow through.

For mobile, keep it careful. Google penalises intrusive interstitials on mobile. Your mobile popup can’t cover the primary content immediately on page load. Use a smaller banner or a delayed popup that’s easy to dismiss. Full-screen mobile popups that fire on page load can trigger a Google ranking penalty. A bottom bar or a slide-in from the corner is safer and still converts well.

A/B test the offer, not just the design. “10% off” versus “free shipping” versus “exclusive access” perform differently by audience. For some audiences, a content-based offer (‘Get our free style guide’) outperforms a discount offer. The popup’s value proposition is usually a bigger lever than its design, timing, or placement.

the fear of annoying visitors is overblown. Data consistently shows that well-designed popups with genuine offers don’t increase bounce rates. The visitors you ‘lose’ from a popup were unlikely to convert anyway.

Double Opt-in vs Single Opt-in

Double opt-in adds a step: subscriber signs up, receives a confirmation email, clicks to confirm. Single opt-in means they’re subscribed immediately after entering their email.

I’d recommend double opt-in for most businesses. Here’s why.

Double opt-in validates email addresses (catching typos and fake entries), prevents spam signups from bots, reduces spam trap exposure, and builds a cleaner list from day one. The subscribers who confirm are genuinely interested. It’s also best practice for GDPR and CASL compliance.

The trade-off is friction. You’ll lose 20-30% of signups who don’t complete the confirmation step. But this number is misleading. Those people either entered fake emails, made typos, or aren’t engaged enough to click one confirmation link. Your metrics improve because you’re only counting real, interested people.

A smart compromise: use single opt-in for purchasers (they gave you real information at checkout, and the transaction serves as verification) and double opt-in for lead magnets, popups, and other signup forms.

One more thing on double opt-in: it’s your single best defence against spam traps and list bombing attacks. A spam trap address can’t click a confirmation link. A list-bombing attack that floods your form with thousands of fake addresses generates thousands of confirmation emails, but none of those addresses get added to your active list because none of them confirm. The protection is built into the mechanism.

Growing from Zero

Growing from 0 to 100 subscribers is harder than growing from 1,000 to 10,000. The first 100 require manual, one-at-a-time effort.

Start with everyone you already know. Existing customers, social media followers, friends, colleagues. Share your signup link in relevant communities (don’t spam, add value first). Post on social media with a clear reason to subscribe. If you have a blog, add signup forms to every post.

The key insight from experienced operators: the first 100 subscribers come from personal outreach, not from systems. After you reach a critical mass (somewhere around 500-1,000 subscribers for most niches), organic growth mechanisms kick in. People share your emails, search engines index your content, referral programmes work because there’s enough audience to create word-of-mouth.

Don’t wait for a big list to start sending. You can generate revenue from email with as few as 100-500 engaged subscribers. The first sale from email often comes from a surprisingly small list.

Noah Kagan (Chief Sumo at AppSumo, 750K+ email list) teaches the ‘Law of 100’: commit to sending 100 emails before judging results. Most people give up after 10-20 sends when they don’t see immediate results. The relationship between sender and subscriber builds over time, and the response rate at email 50 is dramatically different from email 5.

Sam Parr, who co-founded The Hustle and grew it to 1.5 million subscribers before selling to HubSpot, has a useful insight here: spend months getting the voice and format right before investing in growth. Early newsletters should have low subscriber counts but high open rates (40-50%) and high forward rates. If your open rate is below 40% in the early days, you have a content problem, not a growth problem.

List Hygiene

Email lists decay at 22-30% annually. For B2B, the decay rate is even steeper at roughly 2.1% per month, because people change jobs, companies restructure, and addresses become invalid.

A clean list isn’t just nice to have. It directly affects your deliverability, which affects whether your emails reach anyone at all.

If someone signed up six months ago and hasn’t opened or clicked a single email since, they’re dragging down your sender reputation. Inbox providers evaluate your sending at the domain level. If 40% of your list is unengaged, the negative signals from that 40% affect inbox placement for the other 60% who actually want to hear from you.

The sunset flow. Before you remove unengaged subscribers, give them a chance to come back. A sunset flow works like this:

1. Reduce send frequency to unengaged subscribers first. Instead of every campaign, send only your best content.
2. After another 30 days of no engagement, send a re-engagement sequence: 2-3 emails asking “still want to hear from us?” with a clear CTA to stay subscribed.
3. Anyone who doesn’t respond gets suppressed (stop mailing them) but not deleted (keep the data for analytics).

The “breakup email” in this sequence (your last email saying “we’re removing you from the list”) typically generates the highest reply rate, because loss aversion kicks in. Expect 3-10% re-engagement from the sunset flow. The real win, though, is the improved deliverability for everyone who remains.

One example I see cited repeatedly: a brand removed 60% of their list (all unengaged contacts) and saw a 25% increase in revenue from the remaining subscribers, because inbox placement improved dramatically for the engaged segment.

Another way to think about it: unengaged subscribers cost money (most ESPs charge by subscriber count) while providing zero value. If you’re paying for 50,000 subscribers on Klaviyo at roughly $500 per month, and 25,000 of them haven’t engaged in six months, you’re paying $250 per month to damage your own deliverability. Cleaning the list saves money and improves performance simultaneously.

Spam Traps

Spam traps are email addresses that exist specifically to catch senders with poor list practices. Hitting one can devastate your deliverability overnight. Understanding the different types is essential.

Pristine traps. These are email addresses that have never been used by a real person. They’re created as honeypots by ISPs and anti-spam organisations like Spamhaus. The only way to hit a pristine trap is by buying a list, scraping addresses from websites, or using some other method of collecting addresses without consent. ISPs and Spamhaus operate networks of thousands of these addresses. Hitting even one pristine trap can get your IP listed on the Spamhaus SBL (Spamhaus Block List), which blocks your mail at most ISPs globally. Even one hit flags your entire operation.

Recycled traps. These are email addresses that were once used by real people but were abandoned. After bouncing for months or years (the mailbox returns errors because nobody checks it), the email provider reactivates the address as a trap. If you’re ignoring hard bounces and continuing to mail addresses that have been returning errors, you’ll eventually hit a recycled trap. This is why prompt bounce handling matters.

Typo traps. These are addresses at common misspelling domains: gnail.com, gmial.com, yaho.com, hotmial.com. They catch senders who don’t validate email addresses at the point of signup. If someone enters george@gnail.com on your form and you add them without validation, you’ve potentially hit a typo trap.

Role-based traps. Addresses like info@, admin@, sales@, webmaster@ that have been repurposed as traps. These catch senders who are using scraped business contact lists.

Consequences. Getting listed on the Spamhaus SBL is one of the worst things that can happen to your email programme. Most major ISPs reference Spamhaus for filtering decisions. A listing can mean your emails are blocked globally, not just filtered to spam but rejected entirely. Recovery requires identifying how the trap address entered your list, removing it, and requesting delisting, which can take days or weeks.

Prevention. The good news is that spam trap prevention is straightforward:

• Double opt-in. Eliminates virtually all spam trap risk because the address has to receive and respond to the confirmation email. Traps don’t click confirmation links.
• Real-time email validation at signup. Services like ZeroBounce, NeverBounce, BriteVerify, or Kickbox check the email address before it enters your list. They catch typos, disposable addresses, and known traps. Cost is typically $3-10 per 1,000 verifications.
• Regular list cleaning. Run your full list through a validation service every 3-6 months to catch addresses that have gone bad since signup.
• Engagement-based sending. Don’t mail people who haven’t engaged in 6+ months. This prevents recycled trap hits because traps don’t open or click.
• CAPTCHA and honeypot fields on forms. CAPTCHA prevents bot signups. Honeypot fields (invisible form fields that bots fill in but humans don’t) are a lighter-weight alternative that catches automated form fills without adding friction for real users.

List Bombing

List bombing is when an attacker uses your signup form to subscribe thousands of email addresses at once, typically to harass the people at those addresses (who receive unwanted confirmation emails from your brand) and to damage your sender reputation.

Prevention is straightforward: use CAPTCHA or reCAPTCHA on signup forms, implement rate limiting (no more than a few signups per IP address per minute), use double opt-in (so only confirmed addresses receive ongoing emails), and add a honeypot field. Some ESPs like Mailchimp and Klaviyo have built-in bot detection that can help, but your form-level defences are the primary line of protection.

List bombing attacks have become more common in recent years and they can happen to any brand with a publicly accessible signup form. The targets are often surprised because they assume their small brand wouldn’t attract this kind of attack. But list bombing is often automated and indiscriminate. The attackers aren’t targeting you specifically. They’re exploiting any open form they can find.

If you get list-bombed, immediately pause sending to new subscribers, remove the suspicious batch, and check your bounce rates and spam complaints. Contact your ESP’s support team, as they’ve likely seen this before and can help you clean up.

How to detect spam traps in your list

You’ll never know specifically which address is a trap. Trap operators don’t identify individual addresses. What you’ll see are symptoms: a sudden reputation drop in Google Postmaster Tools, a blacklisting notification from MXToolbox, or unexplained placement in spam folders.

If you suspect a trap hit, here’s the diagnostic process:

1. Check Google Postmaster Tools for domain reputation changes (look for a drop from ‘High’ to ‘Medium’ or ‘Low’)
2. Run a blacklist check on MXToolbox to see if your IP or domain is listed
3. Send a seed test through GlockApps or Mail-Tester.com to see where you’re landing across providers
4. Review your most recent list additions. Did you import a batch of old contacts? Add a partner list? Change your signup process?
5. Run your full list through a verification service to identify and remove invalid, risky, and catch-all addresses

Prevention is always cheaper than cure. Double opt-in, real-time validation, and engagement-based sending together eliminate virtually all spam trap risk.

Email Validation Services

If you’re not validating emails at signup, you’re accumulating problems. Here’s a comparison of the major services:

Service	Price per 1,000	Key Strength	Notes
ZeroBounce	~$3-8	AI-powered scoring, abuse detection	Also offers deliverability tools
NeverBounce	~$3-8	Real-time API, bulk cleaning	Strong Zapier integration
BriteVerify	~$5-10	Enterprise focus, CRM integrations	Now part of Validity (also owns Return Path)
Kickbox	~$4-8	Sendex score (deliverability prediction)	Popular with developers
EmailListVerify	~$2-5	Budget-friendly bulk cleaning	Good for large lists on a budget

Use real-time validation at the point of signup (API integration with your form) plus quarterly bulk cleaning of your full list. The cost is negligible compared to the deliverability damage a dirty list causes.

Several community members report using list verification services that caught 5-15% of their list as invalid or risky, and seeing immediate deliverability improvements after removal. If you haven’t run your list through a validation service recently, do it this week. The results often surprise people. Even well-managed lists accumulate bad addresses over time through natural decay, typos, and abandoned accounts.

For real-time validation, most of these services offer a JavaScript API that you embed in your signup form. When someone enters their email and clicks submit, the API checks the address in real time (usually under a second) and either accepts it, rejects it, or flags it as risky. Risky addresses (catch-all domains, disposable email services, role-based addresses) can be accepted with a warning or rejected based on your risk tolerance.

What Not to Do

Don’t buy lists. It violates CAN-SPAM, it destroys deliverability, and the “leads” don’t want to hear from you. Veterans in email marketing forums share story after story of clients who bought lists and needed 3-6 months of rehabilitation to recover. Purchased lists are the number one reason clients come to agencies with ‘broken’ email programmes.

Don’t use dark patterns. Pre-checked consent boxes, hiding the unsubscribe link, making signup mandatory to access content. These tactics might inflate your numbers short-term, but they poison your list quality and can land you in legal trouble under GDPR.

Don’t over-contact without value. The sweet spot for most brands is 1-4 emails per month. Going higher can work if every email delivers value (daily newsletters like Morning Brew prove this), but random promotional blasts five times a week will shred your list. Jay Schwedelson (founder of SubjectLine.com and the GURU Conference with 50,000+ attendees) has emphasised repeatedly that email fatigue is caused by irrelevant content, not by frequency. Brands sending daily but highly segmented emails can maintain engagement rates comparable to brands sending weekly, as long as each email is relevant.

Here’s the surprising data point: multiple analyses show that brands who increased from 1 to 2-3 emails per week saw total revenue increase, even though per-email metrics (open rate, CTR) decreased slightly. The aggregate volume more than compensates. The fear of ‘annoying’ subscribers is the single biggest reason brands leave money on the table. The community consensus from thousands of forum discussions is clear: most brands send too few emails, not too many. People who unsubscribe because you email twice a week were never going to buy from you.

That said, there’s a responsible way to increase frequency. Use engagement-based sending (covered in Chapter 3) so that your most engaged subscribers get more emails while less engaged subscribers get fewer. This lets you send more overall while actually reducing complaints.

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