Proton experienced a global service outage earlier today after a critical cooling failure hit one of its data centers in Frankfurt, disrupting access to Proton Mail and other services.
The company says services have since been restored and that no user data was lost during the incident.
The outage began shortly after midnight CEST, with Proton reporting at 00:09 that it was investigating service availability problems. Engineers identified the cause at 00:38 CEST as a critical cooling failure at the company's Frankfurt data center and began shifting traffic to backup sites.
Recovery started roughly an hour later, with Proton reporting that some services were becoming accessible again. A fix was implemented by 01:57 CEST, after which the company began monitoring the recovery while continuing to restore remaining affected systems.
Proton is a Switzerland-based privacy-focused technology company best known for Proton Mail and Proton VPN. It also operates Proton Drive, Proton Pass, Proton Calendar, SimpleLogin, Proton Wallet, and other services, many of which rely on end-to-end or zero-access encryption to limit access to customer data.
By 02:27 CEST, Proton said the outage had been largely resolved. Some users could still experience delays receiving or sending emails and notifications while the company cleared remaining issues. Proton later updated its status page to say those minor problems had also been resolved and that all systems were operational.
Proton repeatedly stressed that no customer data was lost during the outage.
Proton also clarified that its “no data loss” assurance referred to user content stored across its services, such as emails in Proton Mail, files in Proton Drive, and passwords in Proton Pass, rather than activity logs covered by its privacy policies. The company said this stored data remained intact throughout the outage.
Proton also pointed out that emails sent to Proton Mail users during an outage are generally not immediately lost. Sending mail servers normally queue undelivered messages and retry delivery later, meaning messages may be delayed until Proton's receiving infrastructure becomes available again.
Proton says it will publish a post-mortem on its status page after completing incident cleanup.
Users who continue to experience problems should check status.proton.me before retrying operations repeatedly, particularly email sends or file uploads, as delayed requests may complete once service synchronization catches up.
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