That sounds a bit formalistic and abstract to me. Perhaps you could educate us on which specific threats you think we should pay attention to when choosing between Gmail and Protonmail.
What are some specific threats that Gmail defends us against more effectively than Protonmail?
If Protonmail servers are hacked, it's game over (that could be mitigated by having verified client code, but at this time there's the web client that is served dynamically, and the mobile clients are closed source...). That is where Protonmail are at a huge disadvantage unless they have a really really good security team. Server hacking is done a dime a dozen nowadays.
Off the top of my head I think the number 1 "threat" that Google doesn't protect you from is privacy. They are actively watching your email with algorithms to use for advertising purposes.
On the other hand, they have more resources than anyone else to protect against things like DDOS, nation-state hacking/phishing, and physical disasters. They also have a legion of lawyers to protect against improper legal requests, however they will roll right over for a government if it's legal.
Protonmail is on point with the privacy, but their security engineering team is probably less than 1/10th that of Google's.
From the link: "G Suite’s Gmail is already not used as input for ads personalization, and Google has decided to follow suit later this year in our free consumer Gmail service."
They are definitely still reading your gmail. How else would the spam and other filters work? They can also use it under this policy for anything but "ads personalization". Machine learning, Google product integration, other recommendation not deemed to be ads, refining your google profile, etc. A very narrow scope of exclusion.
Well, one might reasonably ask whether "reading your mail" (as in, running an algorithm on it to try to classify phishing vs non) is a security cost or benefit.
Spearphishing is a huge source of compromise at the moment; antiphishing filters might, in that view, be considered a security feature rather than a security fault.
On the other hand, I have, frankly, never understood these privacy arguments. Is it a privacy violation if someone checks a checksum of my incoming mail against a blacklist? What if they compute a hash of my mail to check the DKIM signature? And if those are OK, why is an ML model more of a problem?
>Is it a privacy violation if someone checks a checksum of my incoming mail against a blacklist?
No, the privacy concern is about the potential for abuse if there is a known place in the world where a very detailed account of all my online (and some offline) activities, contacts, communication and personal interests is stored.
It obviously arouses the interest and desires of criminals, governments, employers, politicians, landlords, insurance companies, creditors, marketers, ex partners, extremists and bigots, journalists, potential mates, researchers, etc.
Some of these groups are overlapping and some of the concerns might only arise in the distant future. Governments change. Ownership of companies changes. Personal circumstances and opinions change, but you can't take anything back once its out.
Spam filters don't need to store all the contents. They can simply store hashes of contents.
So even if someone hacks into the spam filters, they won't be able to reconstruct content from your account. They _might_ have insight into things like word usage, but they won't have reconstructed sentences or the like, a priori.
You can build systems like this without having long-term storage of the content, which protects against data issues for one-time leaks.
Why would the cigar seller ask to show me an ad for a STOP SMOKING CIGARS product? Also as I said, this showed up in Youtube the day after I ordered and the email hit my gmail. Never seen those ads before.
The cigar seller sells its customer list to a data broker or uses a third party service that does the same (e.g. it uses your email address as a user identifier in a third party analytics product). Then advertisers buy that data.
Sometimes hilariously. A few years ago a friend emailed me a barbershop quartet video, and I spent the next couple of weeks getting hairdresser ads ...
Given their vast amounts of information about mail, might their spam filter work by only examining the header? That is, of course, still 'reading' mail - though it may be an acceptable trade off for privacy minded people.
And, if it's being interpreted by a machine, does that really count as reading?
SMTP has headers that are visible to the email provider while the email is in transit. The absence of logs, etc., goes far to mitigate this threat. As an added benefit, there is a lot of anti-spam functionality that can be used with only this metadata available, and only ephemerally. I don't think it's true that zero-knowledge at rest means inability to provide common email provider value adds like anti-spam.
To add to the above post, the headers have to be unencrypted, else they'd have no method to actually send the email. If it were encrypted, they'd have no idea what the address was, or who to bounce it to if the address doesn't exist.
Email headers contain a lot of information. It has the various email addresses, servers involved, ip addresses, time stamps, subject, priority, and things like that.
The body of the email is the only part that gets encrypted when encryption is in use.
You are conflating the SMTP envelope and the mail headers. The SMTP envelope is necessary for delivery, the mail headers are not (the addressee information is duplicated)
There are also false positives than never make it into your spam folder - that just get dropped silently. (I have a friend who's company's GSuite email _regularly_ does this...)
I think the right size of any security engineering team is largely determined by the diversity of threats it has to defend against. Same for the legal team.
So team size alone doesn't convince me one way or the other, even if I were to completely disregard all privacy issues.
I am a Gmail user as is my company, so I do trust them quite a bit. But I feel that Google has a much bigger problem on its hands than Protonmail. Both because of its business model and because Gmail does things like search and spam filtering, which Protonmail cannot do.
What are some specific threats that Gmail defends us against more effectively than Protonmail?