To prevent all emails from Apple Support Communities visit your user preferences page. Set the email preference option for Content I'm following and any others you don't want to OFF then scroll down and hit Save.
If you've already tried that and it doesn't appear to have worked, turn the setting on, save the change, wait say 30 seconds, then turn it off and save again. This should stop all email coming from Apple Support Communities.
If you want to receive email replies to questions you ask without the unwanted messages then you're going to need to change what you follow first.
You're currently following the iTunes for Windows community. Click the link, then click the grey Following button near the top right so that it changes to Follow, or if using an iPhone/iPod touch tap the green text that says Following community so it changes to Follow community in blue. On a computer you may also be able to hover over the link and then unfollow from the pop-up overlay.