Thierry from Sendlens
Founder · Amsterdam, NL
I'm the founder of Sendlens. Before Sendlens I spent years inside ESPs — overseeing campaigns, watching dashboards, and piecing post-send analysis together from CSV exports, API outputs, and Slack threads. Sendlens is the tool I wanted for years.
I write about what we see across the ESPs our customers use — ActiveCampaign, Brevo, and the adjacent stack — the reporting limitations nobody ships around, and the patterns that actually move opens, clicks, and conversions.
Want to compare notes, request an integration, or argue with something I wrote? Email [email protected].
Posts by Thierry
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Industry email benchmarks: 5 reasons to compare yourself to yourself
Industry email benchmarks tell you where the average sender sits, not whether your last campaign was any good. For opens, clicks, and conversions, the only honest comparison is you against you. Here's why, and how to run it.
5 ActiveCampaign reporting limitations marketers hit in 2026
ActiveCampaign is a strong sender. But once operators get past the basic campaign report, five specific gaps keep showing up in our calls — and each one has the same shape: the answer lives outside the ESP.
Newsletter vs promotional email: why the same benchmarks mislead both
The single most common mistake we see in email analytics is comparing a newsletter to a flash sale and treating the gap as performance. Clusters fix the apples-to-apples problem without asking marketers to redo their taxonomy by hand.
The email marketing analytics gap: by design, not by accident
Email platforms are very good at sending email. They're less good at telling you why one email outperformed another. That isn't an accident — it's a consequence of what they were built for.
Email automation analytics: why a flow is a sequence, not a list
Most analytics treat the emails in an onboarding flow as independent campaigns. That's the wrong unit of analysis — and it hides the one question automation teams actually need answered.
Why most email A/B tests don't teach you anything
A/B testing is the default answer to "what should we try next." It also quietly rewards noise as if it were insight. Here's why most email A/B tests teach almost nothing — and what actually produces learning.
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