I don't really register to the "you have to read all the e-mails" camp but when I send someone an e-mail expecting a reply I at least would like to be semi-sure

I don't really register to the "you have to read all the e-mails" camp but when I send someone an e-mail expecting a reply I at least would like to be semi-sure they've had a chance to see it and it not just drowned in a mountain of unread ones requiring me to seek alternative contact methods. Note: I don't expect e-mail to be replied to straight away just when there it time, if it's urgent I will most of the time use alternative contact methods.