Before sharing my email address with some person or some org, I do an MX DNS lookup on the domain portion of their email address. It’s usually correct. That is, if the result is not of the form *.mail.protection.outlook.com, then that recipient is not using Microsoft’s mail server.
But sometimes I get stung by an exception. The MX lookup for one recipient yielded barracudanetworks.com, so I trusted them with email. But then they sent me an email and I saw a header like this:
Received: from *.outbound.protection.outlook.com (*.outbound.protection.outlook.com…
Is there any practical way to more thoroughly check whether an email address leads to traffic routing through Microsoft (or Google)?
I’m w/you on the e2ee, of course. But this requires both people to partake, so the suggestion is broken in most non-p2p situations. In a world where govs, NGOs, and most people are incompetent, e2ee is not generally available. From there, do you want to function at all? You can be 100% dysfunctional if you insist on e2ee. I am almost there, actually. Countless businesses lose my business because they are not on the ball w/security. And gov offices get paper correspondence from me because their digital attempt stinks.
But there are situations where e2ee is not strictly important for a particular situation. Yet I will be damned if I have to dance for Google or MS to get their servers to accept my msgs, all to help the scumbags profit from seeing my payload. So I will send an in-the-clear email to non-FAANG recipients in some cases.