Different stroke for different folks, but I'm still very much in the paradigm where email is more like a letter in the mail, not like a text message, IM, or "please return my call" voicemail. [0]
Of course I recognize that email is often used for time-sensitive matters (like scheduling events), but any time I see an email that is likely to require multiple timely backs-and-forths I'll try to move the conversation to a more suitable medium.
[0] Here I'm referring to solicited emails sent by humans or transactional emails triggered directly by a human interaction. In practice our email inboxes also serve as a general "notifications hub" for all sorts of things including recurring events ("remember to pay your bill") and, of course, unsolicited junk.