Re: User ignore email
You might have your finger on one significant aspect. People no longer read all emails.
"Routine" emails from IT just won't be read. Ditto Health and Safety notices, room changes (at one point bane of my life as participants of a meeting would be waiting somewhere, or time, else )and emails from annoying colleague who might well be right but is annoying. And probably a few other message sources too.
Email saying "Sales Invoice problem," or some such and Bingo, it's open, see link, click.
I do remember failing, some years ago, trying to get the brass to stop sending so many emails because of how it poisons the well. Did it work? Did it fuck!