In the HTC one X mail client there doesn't seem to be a way to move up and down to the next email from an open email (as i could previously do on my Desire). Is there a way to do this that i haven't spotted?
In the Gmail client, you can go to the next or previous mail by swiping right or left.
In the stock Email client, there is an arrow on the menu bar.
You have to turn off "Threaded View" in the email client. Once this is done, the "Menu" drop down will have a next and previous option. Go to the email client and go to Menu > Settings > General settings > Show threaded view. Uncheck this and you are good to go.
Actually if you slide to the right you get the next email. Similarly if u slide to the left u go to the previous one