Email marketing remains one of the highest-ROI digital channels — but only when it's done correctly. Too many businesses invest in email infrastructure and then undermine it with predictable, fixable mistakes.
Here are five of the most common errors we see — and what to do instead.
1. Sending to Your Entire List Every Time
The single biggest open rate killer is blasting every email to every contact regardless of their behaviour or interests. A contact who opened every email last month needs different content than one who hasn't opened in 90 days.
Segment your list by engagement level. Create re-engagement sequences for cold subscribers. Reserve your highest-frequency sends for your most engaged audience. This alone can lift open rates by 15–25%.
2. Weak Subject Lines Written Like Ads
Subject lines that read like marketing copy — ALL CAPS, excessive punctuation, or overtly promotional language — trigger both spam filters and reader fatigue. People receive dozens of marketing emails daily. If your subject line reads like every other brand's, it gets ignored.
Test subject lines that feel personal and specific: "A question about your Q3 pipeline" outperforms "Boost Your Revenue Today!" nearly every time. Curiosity and specificity beat promotion.
3. Ignoring Send Time Optimisation
Most email platforms can now identify when individual subscribers are most likely to open an email. Yet many businesses still send every email at the same fixed time each week. B2B emails generally perform best on Tuesday through Thursday mornings, between 8–10am in the recipient's local timezone — but this varies significantly by industry and audience. Test different send times and let engagement data guide you.
4. Not A/B Testing Systematically
If you're not testing, you're guessing. Subject lines, preview text, sender name, CTA placement, email length — each element affects performance. A/B testing even one variable per campaign compounds into significant improvements over time.
Start with subject lines (the highest impact variable) and test one thing at a time. Use statistically significant sample sizes before drawing conclusions.
5. No Clear Re-Engagement Sequence
Subscribers go cold. It happens. What separates effective email programmes is what happens next. Without a re-engagement sequence, cold subscribers sit on your list indefinitely, dragging down deliverability metrics and skewing your analytics.
A three-email re-engagement sequence — sent 7, 14, and 21 days apart — asking if the subscriber wants to stay on your list, with a clear unsubscribe path, is both effective and responsible. Clean lists perform better than large ones.