keep your left mouse button down and drag across area you want to highlight,if you cant highlight then its problem with email you received,maybe its set (content of message) as background image in that case you can not highlight
Click Settings at the top of any Gmail page, and open the Accounts and Import tab. Click Google Account settings. Click Edit next to My products on the right side. Click Remove Gmail permanently
Click Settings at the top of any Gmail page, and open the Accounts and Import tab. Click Google Account settings. Click Edit next to My products on the right side. Click Remove Gmail permanently