Although I don't use Comcast email I think I know what your problem is. The mail appears in a window that's part of the web page. When you try to scroll, the *whole* page moves down, but the window (that's contains the message you want to read and is part of the webpage) moves down too - but the message that's within that window doesn't move. (Not explained that very well).
So, if you have a window on your webpage that contains your email message and you want to scroll the message (because it's so long) but not the whole webpage you need to use the two-finger scroll.
Instead of using just one finger to scroll the web page (as you normally would) lightly touch inside the window containing the message you want to read with two fingers simultaneously and scroll up and down with these two fingers. It takes a little getting used to but you'll soon get the hang of it. It's a bizarre sort of procedure, but it's a neat 'trick' once you know how to do it. To begin with, until you get it right, you'll sometimes end up still scrolling the entire page or zooming or some combination of both of them, but it soon becomes second nature.
Have fun
Tim
Scotland