Turns out, people lost the ability to have multiple profiles on the internet, and I think this due to costs. None wants to pay both to personal Gmail and to the business Google for Work, and if you have multiple identities, the bill goes up quite quickly, and the ease of use is nowhere to be seen.
I self-host my mail server, and I have a few domain names that all point to the same mail server via MX records in DNS.
A businesswoman once proudly shown me a dumbphone and said that she does not have a personal email, only a corporate one. That persuaded me for a while, until I learned that her husband was prosecuted for money laundering around the same time. So yes, not everyone has email, but those who don't are few and they have very good reasons.
Aside from spam and automated emails, pretty much all email typed interactively in an email client is encrypted between the sender and the receiver.
We could have a long technical discussion here about the opportunistic encryption of STARTTLS or about the market share of Google, Microsoft and Apple, but the reality is that is is protected for all practical purposes that matter to ordinary people. That is, it is impossible to view and modify in transit emails that are written by individuals.
Long gone are the days when you could send a mail from gates@microsoft.com from your personal computer. To start with, port 25 is probably blocked for sending at your ISP. Then, even if you managed to send an email, it will be probably rejected as coming from a residential range of IP addresses. But even if you send a mail from Amazon SES, then the receiving SMTP server will use SPF and DMARC to check if Amazon SES can send emails on behalf of @microsoft.com and it won't.
