The Features mention the Web Clipper.
I've been using the free "Greenshot" since 2013.
[The following is just a cut-paste, so I haven't wasted any time.]
I can take screenshots from anything, including from within emails. There's a flexible rectangle, which means you don't get those annoying full-page captures simply to show the "X" at the top right of your screen (as in Brink's otherwise excellent TenForum tutorials).
Here's he clincher for me (maybe Web Clipper does this). Normally, you can't take a screenshot of a popup. The popup closes as soon as you touch it. The solution is to specify a "capture delay", such as 7000milliseconds. That gives you time to show the popup, arrange the flexible rectangle, then wait patiently for the remaining time. The mouse pointer arrow can be shown or hidden, as an option.