1. You shouldn't "trust" as a basis for security or privacy. Eg for protonmail, Proton can still read your incoming emails if they arrive unencrypted; the only way to avoid that is to send E2EE email, which unfortunately most email is not. You should assume that if they can, then they are.
2. If you have to use proton for whatever reason (can't afford to pay to self-host things, don't know how to and don't have time to learn, etc), it's perfectly fine for everyday use for things that are not particularly sensitive ie you don't have a highly resourced state actor actively trying to obtain that data. Just always keep the first thing in mind. Too many people treat anything that calls itself "encrypted" as a silver bullet.

According to Proton's AI answers:

Proton Mail is designed with a strong commitment to user privacy and security. Here’s what you need to know about the information Proton Mail can provide to law enforcement:

Encryption: Proton Mail uses end-to-end encryption, which means that the content of emails is encrypted on the user's device and can only be decrypted by the intended recipient. Proton Mail cannot read or access the content of your emails.

Metadata: Proton Mail can access certain metadata associated with user accounts, such as:
    Account creation date
    Last login time
    IP addresses used to access the account
    Email headers (sender, recipient, subject line, timestamps)

Legal Process: Proton Mail will only disclose user information to law enforcement if it receives a valid legal request, such as a court order or subpoena, that complies with Swiss law. Proton Mail is subject to Swiss privacy laws, which are among the strictest in the world.

No Backdoor Access: Proton Mail does not have backdoor access to user data. The company is committed to protecting user privacy and will resist unnecessary or overly broad requests for information.

Transparency Reports: Proton regularly publishes transparency reports detailing the number and nature of legal requests it receives. These reports provide insight into how Proton handles requests for user information.

Metadata in the context of Proton Mail refers to the additional information associated with your emails that is not part of the actual email content. While the content of your emails is end-to-end encrypted and only accessible to the sender and recipient, metadata can include the following details:

Account Information:
    Account creation date
    Account status (active, suspended, etc.)

Login Information:
    Timestamps of when you last logged in
    IP addresses used to access your account

Email Headers:
    Sender's email address
    Recipient's email address
    Subject line of the email
    Timestamps indicating when the email was sent, received, or read
    Information about the email's path through servers (though Proton Mail minimizes this due to its encryption practices)

Message Status:
    Whether an email has been sent, delivered, or read (if read receipts are enabled)

Yes, there have been instances where law enforcement agencies have made valid legal requests to Proton, and in some cases, these requests have led to investigations or arrests. However, Proton's transparency reports do not provide specific details about individual cases to protect user privacy and comply with legal confidentiality requirements.

Proton regularly publishes transparency reports that summarize the number and types of legal requests it receives, as well as how it responds to those requests. These reports provide insight into the nature of the requests and Proton's commitment to user privacy.

For example, Proton's transparency reports may indicate the number of requests received from law enforcement agencies, the types of information requested, and whether Proton provided any information in response. However, the reports do not name individuals or provide specifics about individual cases.

If you're interested in learning more about Proton's transparency reports, you can find them on Proton's official website. These reports demonstrate Proton's commitment to balancing user privacy with legal obligations.

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