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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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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