I have spoken to a few people recently, who have called the Amsys Helpdesk, that find the default feature in 10.7 and 10.8 which removes the scrolling bars in different windows, such as Mail and Safari, a bit frustrating. However, it’s not as difficult as you would think in order to turn it back on…
Simply load System Preferences from either the applications folder or the logo and select General.
Within General there are some different settings you can use regarding your custom requirement with the scrolling bars, pick which option you would like and from then on you will be able to see the scrolling bar.
Let us know if this issue affects you and if this quick fix helps.