[prmoustache]

I don't think these things are as important as you think.

RSVP for example. Nobody read or cares who and what people reply. In the last 4 companies I worked for (including one in Switzerland), nobody cared if I accepted or confirmed my attendance to the meeting and would try to call me/force me into a meeting even when my status showed I was on another shsring my screen. And nobody seems to respond nowadays nor check calendars for availability and avoiding conflicts.

[arcza]

But what about push notifications to mobile? I'm not aware of anything that handles this as well as Exchange ActiveSync. it's reasonable that you get an email within sub 1 minute latency, not 15 min polling.

[prmoustache]

The IMAP protocol has an IMAP IDLE extension for that purpose.

But is that use case really common in practice? With chat tools people don't tend to use email for instant messaging (well, appart from deltachat users, which can be a solution too!) and my experience is that it doesn't even work like that / that well for office 365 users. I am regularly told on teams that an email has been sent to me (same org and same region) yet it still takes more than a couple of minutes to have it visible on my desktop outlook client.