Youtube consists of channels and users. Each user on youtube has their own channel. Registered users can subscribe to any youtube channel and get notified for latest videos from those channels.
If you want to receive email notification when certain user or channel posts a video specifically, you can do this by following these simple steps.
Goto the channel for which you want to receive each new posted video update in your email. To make things simple for you there is option on each video page to get notification of new uploads by a particular youtube channel via email. When you are at that channel, click on subscribe. It will slide sown a bit and show you an option saying “Also email me for each new upload” (shown in following image – from random youtube channel)
Select the option saying also email me for each new upload and save settings.
Now you will receive an email notification whenever this users adds new video to his channel!