Cover letter
Dear Proton Product hiring team,
I’m Charles Berthillon, founder of FlowMail. Before that I ran complex product and delivery programmes in banking and consulting.
I spent a year turning my last six years of work into an email product. I used Proton as the reference for what a can become. I don’t want to scale that alone under early VC pressure. I want to put that craft and judgment behind Proton Inbox, where the trust and scale already exist. I’m applying for Head of Product (Mail) / Group Product Manager (Inbox), and I’m delivering this letter in person at your Geneva office.
Why Proton, now
Proton has proved that privacy can win users at scale. The next fight is different: become the daily inbox without giving up that trust. That means auto-organisation, multi-inbox (including Gmail alongside Proton), stronger search and mobile, and a clear path from attention to usage, retention, and .
Mail is the most-used daily app for organisation and communication. Inbox strategy matters now: turn that attention into lasting habits, growth, and ARR, without giving up Proton’s privacy edge.
Why me
I am an atypical founder-executive profile, not a career consumer PM from Big Tech.
At FlowMail I own vision, roadmap, and shipping end to end: Gmail and Microsoft Graph, OAuth, deliverability, compliance (including Google CASA), and the cross-functional work of product, growth, and trust.
This focus started earlier. Between 2019 and 2022, while launching the neobank 3A Circle and an open-banking payment factory, long before today’s AI wave, my main concern was the . I wanted to work inside the apps people already use, not force another download. Email became the natural tool. We also faced email security in practice: deliverability, spam, and what it takes for a message to be trusted.
In consulting, I led teams of product managers, business analysts, and testers on programmes such as Société Générale Private Banking’s tax hub (SaveTax) and PMS AAA. I set priorities, sequenced work with engineering, and brought stakeholders with me.
At Dexia’s CEO Office and later as COO of a family-office and WealthTech platform (around €15Bn AUM), I often worked without a direct hierarchical mandate. I had to convince staff in external organisations, align senior leaders, and still own outcomes under real P&L and governance pressure.
That mix of email craft, technical fluency, and executive tradeoffs is what I would bring to Inbox strategy and to coaching a PM team as the scope expands.
Why leave FlowMail
FlowMail was deliberate: one year to concentrate my experience into a live product. The vision attracted VC interest (email as a daily marketing opportunity, then email banking, then the broader cloud stack). Scaling alone is too hard, and I was not willing to be enslaved to venture capital from day one.
Proton already has the users, the brand, and the independence I respect. I used Proton as a for a reason. I want to help Inbox win the productivity fight on the product that has already earned the right to do it.
I am based in Lausanne, available for Geneva and for travel across Proton’s European hubs. I would welcome a conversation on Inbox strategy, roadmap, and how I would raise the bar for the PM team.
Yours sincerely,
Charles Berthillon
Enclosure: CV