[derfniw]

100% agreed.

I try to treat email as any other letter I recieve(1). Meaning that the sender can only expect an instant reply if I know beforehand the mail is coming and urgent. The same way one would rapidly reply to an urgent letter one is expecting, but easily take a day or more to reply to, or even open, a non urgent letter.

If you need to get a hold of someone directly you should use your phone (to call them). If they don't pick up their phone, leave a voicemail or send an sms.

(1) Registration confirmations / new password emails are an obvious exception here.

[snogglethorpe]

...and of course even voicemail / SMS are not guaranteed to be seen anytime soon!

[If at all; I know plenty of people who simply never check their voicemail...]