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Proton Mail Discloses User Data Leading to Arrest in Spain
(restoreprivacy.com)
This is a most excellent place for technology news and articles.
They mean encrypted at rest. As in, Proton cannot hand over a copy of all your emails to a law enforcement agency, they don’t have access.
This means law enforcement would have to capture an unencrypted email in transit, or obtains your emails from either recipient individually.