Proton Mail security has been tested in public more often than almost any service I write about, and IMO, that is exactly why I trust it more rather than less. A company that posts its own breach scares, court orders, and patched bugs is a company with nothing buried. So here is the full run, from a CERN lunch table in 2013 to the account suspensions that blew up last September.
The CERN origin story (2013 to 2014)
The project started in 2013 in Geneva, dreamed up by Andy Yen, Jason Stockman, and Wei Sun, three researchers who met at CERN. The timing was not random. Snowden had just blown the lid off NSA surveillance, and Lavabit, the encrypted service he used, had been forced to shut down rather than hand over its keys. Proton’s pitch was simple: end-to-end encryption, servers in Switzerland, zero-access design so even Proton cannot read your mail.
Public beta opened on May 16, 2014. They expected a few hundred signups a month. They got around 10,000 in a single weekend, the servers buckled, and signups went to an invite-only waitlist while they scrambled for capacity. Then the money got weird. During the summer Indiegogo campaign (which pulled in 550,000 dollars from over 10,000 backers), PayPal froze the account and held roughly 250,000 dollars, reportedly questioning whether encryption was even legal. The freeze lasted a day before the backlash reversed it. That is the kind of start that tells you what kind of company you are dealing with.
The 2015 DDoS attack, still the big one
November 3, 2015, is the date every Proton old-timer remembers. Just before midnight, Proton got a blackmail email from a group calling itself the Armada Collective, followed by a DDoS that knocked it offline for about 15 minutes. The next day, it escalated into something else entirely: a coordinated assault on Proton’s ISP and data center that exceeded 100 Gbps, targeting routers in Zurich, Frankfurt, and beyond, taking down hundreds of other companies as collateral.
Under pressure from the datacenter and other affected parties, Proton paid the ransom, around 15 bitcoin, roughly 6,000 dollars at the time. The attacks kept coming anyway. Paying was a mistake, and Yen got hammered for it by the security crowd, a call he later said he regretted. The service came back after roughly six days; users chipped in over $50,000 for proper defenses, and Proton has relied on Radware’s DDoS protection ever since. A smaller burst attack in June 2018 caused short outages, but nothing like those in 2015.
The actual code bugs (the part people forget)
DDoS is brute force. The more interesting question for an encrypted mailbox is whether the code itself leaks. Two cases stand out, and both got patched.
First, CVE-2021-32816. The old AngularJS web client had a regular expression denial-of-service flaw (a ReDoS, classified as CWE-400) in the routine that parsed public keys from a message. GitHub Security Lab found it with a CodeQL query and filed it as GHSL-2021-027. Proton fixed it in March 2021, and the CVE went public that May. Low drama, no exploitation, but a clean example of the kind of bug that hides in a regex nobody looks at twice.
Second, and more serious, the 2022 cross-site scripting chain. Researchers at Sonar found client-side flaws that could let an attacker bypass DOMPurify, the sanitizer Proton uses to scrub incoming HTML, by exploiting differences between how browsers parse HTML and SVG. In plain terms: if someone got you to open a booby-trapped email, they could potentially run a script inside the web app and read your decrypted mail or send as you. That is the nightmare scenario for end-to-end encryption, because perfect math does not help if the page rendering it gets hijacked. Sonar disclosed it privately in June 2022; Proton shipped the fix within weeks (repo on June 15, production by early July); and the public write-up only landed in September 2023. No known abuse in the wild. It is also a good reminder that even a privacy-first service born of the painful early years of email encryption is still a web app with web-app problems.
Worth saying: Proton runs a published vulnerability disclosure policy and a bug bounty program, and maintains a page documenting fixes. For a company founded by CERN people, peer review is basically the house religion.
When the law showed up (the cases that matter more than the bugs)
For a privacy service, the scarier incidents are not the crashes; they are the moments it handed something over. Three of them stick.
In 2021, the French climate activist. Acting on a Swiss order that arrived via Europol from France, Proton logged and handed over the IP address of a Youth for Climate activist, leading to an arrest. The backlash was brutal because Proton’s own site had bragged that it kept no IP logs, a language it quietly deleted afterward. Yen’s clarification was uncomfortable but honest: if you break Swiss law, a Swiss company can be compelled to log your IP, and that is how it works. The partial silver lining came in October 2021, when Proton won a Swiss ruling that email providers are not telecom companies and so are not bound by telecom data-retention rules.
2024, the Catalan case. Proton handed Spanish police a recovery email address tied to a Democratic Tsunami account during a terrorism investigation, which helped identify the user. Same lesson: the encryption held, but the metadata you bolt onto an account, recovery email, and IP, is the soft underbelly.
2025, the Phrack mess. Two security researchers working on a Phrack article about a North Korea-linked intrusion had their Proton accounts suspended right after they used them to notify victims. Proton first cited a CERT alert and a terms-of-service violation, the story exploded online, and Yen eventually reinstated the accounts, explaining the suspensions targeted hacktivist activity rather than journalism. Messy, and a reminder that “violates our terms” is a very blunt instrument.
Blocks, outages, and the milestone reel
Governments have taken swings, too. Belarus briefly blocked Proton in November 2019, Russia blocked it in January 2020 over accounts allegedly sending bomb threats, and in April 2025, a Karnataka court ordered India to block it after a harassment complaint. The biggest self-inflicted wobble was on January 9, 2025, when a spike in database connections triggered a global outage affecting Mail, Calendar, VPN, Drive, Pass, and Wallet for a few hours. No breach, just downtime, though paying users were not thrilled about the communication.
Through all of that, the product kept shipping. Quick reel: open-sourced web client with v2.0 (2015), public launch out of beta with v3.0 (2016), a Tor onion site (2017), the Bridge for Outlook and Thunderbird (2017), full PGP and address verification (2018), the SimpleLogin acquisition and the proton.me domain (2022), the rebrand from ProtonMail to Proton Mail (2022), a real desktop app (2024), the Scribe writing assistant (2024), and somewhere past 100 million accounts. In July 2025, Proton even started moving its AI infrastructure to Germany and Norway, openly saying it no longer fully trusts where Switzerland’s privacy law is heading, which is a wild twist when you remember the whole pitch was built on Swiss soil. It is the same question driving the data sovereignty fights I keep writing about: less about who holds your data, more about where it physically sits, far from the ad-funded inbox model Proton was built against.
So, do I still recommend it?
Yes, absolutely. Not because Proton is flawless, nothing is, but because its failure modes are public and its encryption has never actually been the thing that broke. The bugs got patched. The DDoS got mitigated. The handovers were metadata under court order, never decrypted mail, which is exactly the line the architecture promises to hold. If your threat model includes a nation state, pair it with the Tor site or a VPN, and stop attaching a real recovery email. For everyone else who is just tired of trusting their data to someone else’s servers, it stays the most credible inbox out there.