Latest / The Email Marketing Podcast with Fexingo: Newsletters, Open Rates, and Subscriber Growth / How Email List Validation Cut Bounce Rates for a SaaS Startup
Transcript
- Lucas: So Luna, you know how we're always saying that the list is the most valuable asset in email marketing? Well, today we're going to talk about what happens when that asset quietly turns into a liability. Luna: Oh, I have a feeling I know where this is going. Bounce rates, right? Lucas: Exactly. And not just any bounce rate story. There's a B2B SaaS startup we'll call Nimbus Analytics — a team of about twenty, selling a data visualization tool to mid-market companies. They were growing their list aggressively through webinars and gated content, but their campaign performance was tanking. Open rates hovering around twelve percent, and their domain was starting to get flagged. Luna: Twelve percent is brutal. What was the bounce rate? Lucas: It had crept up to almost seven percent. And the thing is, they didn't notice it at first because they were so focused on list growth. They were adding maybe two thousand contacts a month, but they never checked the quality of those addresses. Luna: So what was in there — typos, old work emails, people who just made up an address to get the whitepaper? Lucas: All of that. Plus, they had a lot of catch-all domains — you know, addresses on servers that accept everything and then silently drop it. And some really old contacts from their early days who had long since changed jobs. Luna: Classic list rot. So what did they do? Lucas: They decided to run a validation pass before every send. They picked a third-party verification tool, integrated it with their ESP, and set it to check all new signups in real time. Then they also ran a one-time cleanup of their entire list of forty thousand contacts. Luna: Forty thousand is a decent size. What did the cleanup turn up? Lucas: About eleven percent of the list was invalid or risky — bad syntax, disposable addresses, known spam traps, plus a bunch of catch-alls. They removed those. Within two months, their bounce rate dropped from nearly seven percent to under one percent. That's a 38 percent relative reduction in bounces per campaign. Luna: Wait, 38 percent — but you said it dropped by six percentage points. That's a huge relative improvement, but the absolute numbers are small. Still, for deliverability, that shift is massive. Lucas: Right. And the effect on sender reputation was almost immediate. Their domain's spam complaint rate fell, and they started seeing their emails land in the primary inbox instead of promotions or, worse, spam. Their open rates climbed back to around twenty-two percent. Luna: That's a tangible payoff. But I bet there's a cost side to this too — not just the tool subscription, but the risk of removing good contacts by mistake. Lucas: That's a fair pushback. Validation tools aren't perfect. They can flag a valid address as risky, especially if it's on a lesser-known domain. So you have to use them intelligently. Nimbus didn't hard-delete everything the tool flagged. They set up a 'risky' category for contacts that had a lower confidence score, and they sent those a one-time re-engagement email before deciding. Luna: Smart. So you're not throwing the baby out with the bathwater — you're giving people a chance to prove they're real. Lucas: Exactly. And that's the nuance a lot of marketers miss. List hygiene isn't just a one-time purge. It's a process. You need to decide on your tolerance for false positives versus the risk of keeping bad data. Luna: And speaking of keeping the lights on, I'm reminded that this podcast itself runs on listener support. If these marketing conversations have sparked something you've actually used — a new way to think about your list, a tactic you tried — a couple of dollars a month is genuinely what keeps these going. Buy me a coffee dot com slash fexingo, if you've gotten something out of them. Lucas: Yeah, it really is that simple. No ads, no sponsors — just listeners who find value here. And we appreciate every bit of it. Luna: So back to Nimbus — after they cleaned the list, did they change anything about how they grow it going forward? Lucas: That's the key part. They didn't just clean and forget. They put verification at the point of capture. So every new signup gets checked in real time, and if it's clearly invalid, the form rejects it with a message like 'please double-check your email address.' That alone cut their invalid signups by about 60 percent in the first month. Luna: So it's a double win — you keep your list clean from the start, and you also save on the cost of sending to bad addresses. Lucas: Exactly. And that's a real cost, too. Most ESPs charge based on list size or sends. If you're sending to a list with ten percent junk, you're paying for those bounces and those spam traps. It's not just a deliverability problem — it's a budget problem. Luna: Now, what about the catch-all domains? Those are tricky because they don't bounce at the moment of sending. How do you deal with those? Lucas: Good question. Catch-alls are sneaky because the address doesn't bounce immediately — the server accepts it and then silently discards it. That can inflate your 'delivered' rate while crushing your engagement metrics. Nimbus had a lot of those, especially from older signups. Their validation tool flagged them as 'risky,' and they used a re-engagement campaign to see who actually opened or clicked. Luna: So you're using engagement as a proxy for validity. That's a nice fallback when the technical check isn't conclusive. Lucas: Yeah. And it ties into a broader principle: your list should be people who want to hear from you. If someone hasn't opened an email in six months, even if their address is technically valid, they're dragging down your metrics. That's why Nimbus also set up a sunset policy — contacts who hadn't engaged in ninety days got a final 'do you still want to hear from us?' email, and if they didn't respond, they were moved to an inactive list. Luna: And that's different from just deleting them, right? Because you can potentially re-engage them later with a different campaign. Lucas: Right. Inactive doesn't mean gone forever. It means they don't get your regular sends, so they don't hurt your overall engagement rate. But you can still try to win them back with a targeted campaign or a special offer. It's a more strategic approach to list management. Luna: So for our listeners who want to do something like this, what's the first step they should take tomorrow morning? Lucas: The first step is simple: pull a report on your last three campaigns and look at your bounce rate. If it's above two percent, you have a problem. Then, pick a reputable verification service and run your list through it. Don't get overwhelmed by the number of flags — start by removing clear hard bounces and known spam traps. That alone will give you a boost. Luna: And what about the cadence — how often should you validate? Monthly? Quarterly? Lucas: The industry sweet spot is every quarter for a list that's actively growing. If you're adding a lot of new contacts, you might do a mini-check every month on just the new additions. Nimbus now validates all new signups in real time and does a full-list scrub every quarter. That's kept their bounce rate consistently under one percent for the last six months. Luna: That's a great benchmark. Under one percent is achievable if you're disciplined. Lucas: Absolutely. And the payoff isn't just better deliverability — it's also better relationships with your subscribers. When you send fewer emails to people who don't want them, the ones who do get them are more engaged, and that shows up in your open rates, click-throughs, and ultimately your revenue per email. Nimbus saw their revenue per campaign increase by about 15 percent after the cleanup, simply because they were reaching the right people. Luna: That's the kind of result that gets a CFO's attention. So, to sum up: clean your list, validate at the point of capture, and set a regular hygiene cadence. That's a solid foundation for any email program. Lucas: And the key takeaway? Your list is an asset, but only if it's accurate. A smaller, cleaner list will almost always outperform a bigger, messier one. So don't be afraid to prune. Your deliverability — and your subscribers — will thank you. Luna: Well said. And if you want to see how your own list stacks up, start with that bounce rate check today. We'd love to hear how it goes — you can find us on social and let us know. Lucas: And if you found value in this episode, consider supporting the show on Buy Me a Coffee. It genuinely keeps us going. Until next time, keep your lists clean and your emails landing in the right inbox.