I used neomutt for that one example, but the other error modes happen to me regularly on macOS with the system mail client. For example, I regularly (~1/week) run into services that expect the verification email to be opened in the same browsing session, but Chrome "helpfully" picks a different profile.

(The point about neomutt was not that services should support my particular pathological case, but that graceful degradation is important everywhere. It used to be common to send multipart emails for exactly this case, but I've seen more and more services choose not to.)