Latest / The Email Marketing Podcast with Fexingo: Newsletters, Open Rates, and Subscriber Growth / How Email List Deliverability Testing Prevents Spam Folders
Transcript
- Lucas: You spend hours crafting the perfect email. You segment the list, personalize the subject line, and obsess over the call to action. Then you hit send, and half your audience never sees it because it landed in the spam folder. Luna: Right, and most marketers don't realize that deliverability isn't just about not bouncing. It's about actually hitting the inbox. Today, we're going to talk about a specific process: deliverability testing before you send. Lucas: Exactly. I want to start with a concrete example. A mid-sized B2B SaaS company I work with — about 50,000 subscribers — was seeing an inbox placement rate of around 88 percent. That means 12 percent of their emails were going straight to spam or promotions tabs. For a company that relies on lead nurturing, that's a lot of lost opportunity. Luna: Twelve percent — that's six thousand subscribers per send. So what did they do? Lucas: They implemented what's called a seed list test. Before every campaign, they send a copy of the email to a set of test email addresses across all the major providers — Gmail, Outlook, Yahoo, iCloud. Then they use a tool that tells them exactly which inbox the email landed in, and what the spam score is. Luna: So it's like a canary in a coal mine. You catch issues before they affect your whole list. Lucas: Precisely. In their case, the tool flagged that their email had a high spam score because of a broken DKIM signature. DKIM is an authentication protocol that proves the email hasn't been tampered with. Their IT team had recently migrated email servers and forgot to update the DKIM key. So the signature was failing, and Gmail was penalizing them. Luna: And that's something you'd never catch just by looking at your email template. It's a backend issue. Lucas: Right. Once they fixed the DKIM key and added a DMARC policy — which tells receivers what to do if authentication fails — their inbox placement jumped to over 98 percent within two weeks. The key was that they tested before each send, not after. Luna: So deliverability testing is really about proactive monitoring. What are the other common issues that seed list tests catch? Lucas: Several. One is content-based triggers. For example, if your email contains phrases like 'free money' or 'act now' in the body, that can trigger spam filters even if your authentication is perfect. Another issue is image to text ratio. If your email is mostly images with very little text, it looks like a spammy promotional piece. A seed list test will show you the spam score breakdown and let you adjust. Luna: And for listeners who don't have a big budget, are there free or low-cost tools that can do this? Lucas: Absolutely. There's Mail-Tester.com — you send an email to a unique address, and it gives you a score out of ten along with specific issues. Also, GlockApps has a free tier for a few tests per month. And SenderScore.org lets you check your sending IP's reputation for free. But the most important thing is to establish a routine — test every campaign, not just once a quarter. Luna: That makes sense. But what about the difference between deliverability and delivery? I think some marketers confuse the two. Lucas: Good point. Delivery just means the email was accepted by the receiving server. It didn't bounce. Deliverability means it went to the inbox, not the spam folder. You can have a 99 percent delivery rate but only a 70 percent deliverability rate. That's a disaster hidden behind a good-looking metric. Luna: So if you're only tracking bounces, you're missing the bigger picture. You need to track inbox placement. Lucas: Exactly. And the only way to measure inbox placement reliably is to use these testing tools. Some email service providers offer built-in deliverability diagnostics, like Mailchimp's Inbox Preview or Constant Contact's Deliverability Tool. But they may not be as granular as dedicated tools. Luna: I want to circle back to the B2B company. After they fixed DKIM and DMARC, how did they maintain that 98 percent rate? Lucas: They created a pre-send checklist. Every campaign goes through: verify DKIM and SPF records are valid, check the spam score with a seed list test, review the image to text ratio, and scan for trigger words. It takes about 15 minutes per campaign. And they also monitor their sender reputation weekly using SenderScore. If the score drops below 80, they investigate immediately. Luna: That's a great discipline. And I think for a lot of marketers, the idea of testing every send sounds like a burden. But when you consider the cost of 12 percent of your list never seeing your email, the ROI is huge. Lucas: Absolutely. And it's not just about revenue. It's about protecting your sender reputation. If you send a campaign with a high spam score, it can damage your IP's reputation for future sends. Even if you fix the issue later, it takes time to recover. Luna: So it's a compounding problem. One bad send can hurt you for weeks. Lucas: Right. That's why we recommend a monthly deliverability audit in addition to pre-send testing. Audit your authentication records, check your spam complaint rate — which should be below 0.1 percent — and review your list hygiene. Remove subscribers who haven't engaged in six months. All these factors feed into how email providers treat your mail. Luna: And let's not forget the role of engagement. Even with perfect authentication, if people don't open your emails, that tells Gmail your content isn't wanted. Lucas: Yes. Engagement is a big part of the algorithm. So deliverability testing is just one piece of the puzzle, but it's a piece that's often ignored. If you're not testing, you're flying blind. Luna: You know, speaking of practices that improve the show — we've been talking about how testing helps deliverability, and that's exactly the kind of practical insight we try to bring every episode. If these marketing conversations have sparked something you've actually used, we'd love it if you considered supporting the show. Lucas: Yeah, we deliberately keep this podcast ad-free. No sponsors, no sponsored segments. It's just us sharing what we've learned. If that model resonates with you, there's a simple way to help keep it going. Luna: It's at buy me a coffee dot com slash fexingo. No pressure, just a way to support if you find value in what we do. Lucas: And now back to deliverability. One more tool I want to mention — there's a service called MXToolbox that lets you check your DNS records for free. You can verify your SPF, DKIM, and DMARC records are set up correctly. That's a quick way to start. Luna: Great recommendation. So what's the one takeaway you want listeners to remember from this episode? Lucas: Test before you send. Use a seed list tool, check your spam score, and verify your authentication. It takes less than 20 minutes and can save you from losing a huge chunk of your audience. Inbox placement isn't a given — you have to earn it. Luna: And if you already have a deliverability problem, start with an audit. Fix your authentication, clean your list, and then test every send going forward. Lucas: Exactly. We'll include links to the tools we mentioned in the show notes. Next time, we'll talk about how to recover from a deliverability crisis — what to do if your domain has been blacklisted.