A total cooling failure at Proton’s Frankfurt data centre triggered a widespread outage on 27 August, disrupting Proton Mail and other Proton services.
According to Proton’s post-incident report, cooling failed shortly after 11pm CEST on 26 August. The temperature in the server room climbed from about 21.8°C to 51.9°C in under 30 minutes, with some sensors recording air temperatures of 60°C. Servers and networking equipment began shutting down as temperatures rose.
The incident became user-facing around midnight after both the primary and backup network switches on a critical rack failed. Proton said database failover required human supervision, contributing to a longer recovery. Most services were restored for most users by around 1.30am CEST, with remaining systems recovering by roughly 2am.
Proton said no emails were lost, although incoming and outgoing mail was delayed during the disruption. The company later traced the cooling failure to maintenance involving air-filter replacement on both redundant air compressors. Proton said the data-centre operator carried out the work without prior notice and did not immediately communicate the cooling failure.
It is the second cooling-related email outage in a fortnight. Namecheap took hosting, Private Email and DNS management offline on 13 August after a cooling failure at the RadiusDC Phoenix data centre. In both cases the failure sat with the facility rather than the email platform, and in both the operator’s decisions determined how long recovery took.
Proton is now working on additional database resilience and infrastructure capacity intended to reduce dependency on a single site. Its status page currently reports Proton Mail and other services as operational.
