Three minutes after her on-line music lesson was supposed to start, DD tells me I've forwarded to her email an out-of-date Zoom link. I know I haven't, but send it again. Altogether four times in the ensuing chaos. But no matter how many times I forward the link, there is only one (already read) email in her inbox. And when you open it, it contains the old link.
Eventually I realise there's a number next to the email header, which is going up every time I send an email. The header represents every email that's ever been sent with the same header. Including one from three months ago with the old link. Ok. But when I click on the header, and scroll down, I can't (in my panic) quickly and easily tell where one email ends and the next starts, and the only email body I can see is the one containing the obsolete link.
The situation is resolved for the time being when I give her my (identical) tablet to use, where everything works as it should.
During subsequent investigation I find that the difference between my gmail and hers is that she has conversation view on, the google default. It turns out Conversation view list emails (that it groups by header) in chronological order, i.e. oldest-first, the opposite of what I expect from 99.999999999999% time of time I use email. So when I click on the header at the top of her inbox that's supposed to contain the message I've just sent, I initially see the text from a three-month-old message with the same header. All the newer emails are further down, and collapsed, so you can't see their text. There's a tiny icon you need to find with your finger to expand so you can see the text of the actual latest email, the single most obvious thing someone clicking on the header would have wanted to see.
I now remember that I turned off conversation view for myself when it first appeared, because it was a complete and utter nightmare. In an email conversation in which every message sent by either party quoted the whole previous conversation, as people usually do, the text of the whole email conversation up to that point was repeated within every mail it grouped together. So if you expanded everything, what was one message in the actual conversation got displayed over and over, once for each time it had been quoted. The order of messages you saw as your scrolled down reversed over and over, with patches of normal reverse-chronological order embedded within a higher framework of chronological order. It was impossible to work out what was a reply to what, or even what the last message/reply was, without a forensic examination of dates.
I don't think whoever invented conversation view should be executed, innovation is sometimes a good thing, but AIBU that whoever decided to make it the default needs to be shot?