If you want to see "how many machines have them installed." - this is simply impossible & not even the right approach.
The right approach(Safe web fonts) would be to use @font-face
fetching fonts from users local machine(Windows/MAC pre-installed) using the local()
to fetch from the users pre-installed fonts.
font-face {
font-family: 'myFont';
src: local('Verdana');
src: local('Arial');
src: local(sans-serif);
//result would be - font-family: 'Verdana', 'Arial', sans-serif;
}
The location in any Windows users machine from where the fonts are being pulled is:
C:\Windows\Fonts
The location in any MAC users machine from where the fonts are being pulled is:
/Library/Fonts/
You could see all other pre-installed fonts here as well.
You can check from these, all the common fonts that are pre-installed on Windows & MAC
http://www.ampsoft.net/webdesign-l/WindowsMacFonts.html
http://web.mit.edu/jmorzins/www/fonts.html
UPDATED
If sendgrid is stripping all your embedded styles then use inline styles instead on your elements/body.
<body style="font-family: 'myFont'; src: local('Verdana');">...</body>
There are also some good inliner out there that will convert your embedded CSS to inline CSS.
Zurb email inliner - http://foundation.zurb.com/emails/inliner.html